Merge pull request 'docker-compose.public.yml: значения по умолчанию для jambocheck.com (деплой без .env)' (#15) from fix/public-compose-defaults into master

Reviewed-on: #15

.dockerignore

@@ -0,0 +1,9 @@
+.git
+.idea
+.vscode
+**/node_modules
+**/build
+**/dist
+**/.gradle
+**/.angular
+*.log

.drone.yml

@@ -0,0 +1,47 @@
+# Docker image of reactive-mail-server — like htop-web: Drone builds backend/Dockerfile,
+# master pushes it to the Gitea container registry of jambotron.com.
+#   pull request  -> build only (image is not pushed)
+#   push master   -> gitea.jambotron.com/jambotron_gang/reactive-mail-server:latest and :<commit 8>
+# Drone secrets of this repo: REGISTRY_USERNAME, REGISTRY_PASSWORD (Gitea user with write:package in jambotron_gang)
+kind: pipeline
+type: docker
+name: build-test
+
+trigger:
+  event:
+    - pull_request
+
+steps:
+  - name: build-test
+    image: plugins/docker
+    settings:
+      dockerfile: backend/Dockerfile
+      context: .
+      repo: gitea.jambotron.com/jambotron_gang/reactive-mail-server
+      dry_run: true
+---
+kind: pipeline
+type: docker
+name: build-and-push
+
+trigger:
+  event:
+    - push
+  branch:
+    - master
+
+steps:
+  - name: build-and-push
+    image: plugins/docker
+    settings:
+      dockerfile: backend/Dockerfile
+      context: .
+      registry: gitea.jambotron.com
+      repo: gitea.jambotron.com/jambotron_gang/reactive-mail-server
+      tags:
+        - latest
+        - ${DRONE_COMMIT_SHA:0:8}
+      username:
+        from_secret: REGISTRY_USERNAME
+      password:
+        from_secret: REGISTRY_PASSWORD

README.md

@@ -13,6 +13,7 @@
 ```
 
 - **Приём (SMTP).** Команды разбираются по строкам (`LineBasedFrameDecoder`): работает и пачка команд в одном пакете, и строка, разорванная на два пакета. Письмо сохраняется или ставится в очередь **до** ответа `250`; если сохранить не удалось — `451`, и отправитель повторит. Работа с базой и DNS идёт не в сетевом потоке.
+- **TLS.** `STARTTLS` на порту SMTP (RFC 3207) и, если задан `SMTPS_PORT`, неявный TLS (RFC 8314, обычно 465); TLS 1.2/1.3. После `STARTTLS` сессия начинается заново (новый `EHLO`), а команды, присланные открытым текстом вместе со `STARTTLS`, не выполняются — соединение закрывается (CVE-2011-0411). `AUTH` предлагается только внутри TLS (или без него при `SMTP_AUTH_WITHOUT_TLS=true`). Сертификат — свой (`MAIL_TLS_CERT` + `MAIL_TLS_KEY`, например Let's Encrypt) или самоподписанный: создаётся один раз в `MAIL_TLS_DIR` и потом переиспользуется. Свой сертификат сервер перечитывает сам, когда файлы меняются (проверка раз в минуту): обновлённый Let's Encrypt подхватывается без перезапуска, недописанный файл не ломает TLS — остаётся прежний сертификат.
 - **Не открытый релей.**
   - Письмо на свой домен принимается от кого угодно.
   - Письмо на чужой домен — только после `AUTH`, иначе `550 5.7.1 Relaying denied`.
@@ -30,6 +31,17 @@
 - **DKIM.** Подпись — `utils-mail-dkim` (rsa-sha256, relaxed/relaxed), проверка входящих — Apache James jDKIM по ключу из DNS отправителя. Ключ создаётся один раз в `DKIM_KEYS_DIR`, запись для DNS печатается в лог при старте: `TXT <selector>._domainkey.<domain>`.
 - **Права.** Письма, папки и вложения отдаются только владельцу (чужие — `404`). Регистрация по умолчанию закрыта, ящики — только в своих доменах.
 
+## IMAP
+
+Почтовые программы (Thunderbird, почта на телефоне) работают с теми же ящиками, что и веб-почта.
+
+- **Порт** `IMAP_PORT` (3143) со `STARTTLS`, и неявный TLS на `IMAPS_PORT` (993), если задан. Сертификат тот же, что у SMTP. Вход (`LOGIN`, `AUTHENTICATE PLAIN`) — только внутри TLS, без него сервер отвечает `LOGINDISABLED`.
+- **Возможности:** IMAP4rev1, LITERAL+, IDLE (новые письма приходят сами, проверка раз в 5 с), UIDPLUS, MOVE, UNSELECT, NAMESPACE, SPECIAL-USE (Отправленные, Черновики, Корзина, Спам клиент находит сам), ID.
+- **UID** выдаёт база (триггер): письмо, перенесённое в папку из веба или по IMAP, получает новый, больший UID — клиент его не пропустит. Флаги `\Seen`, `\Flagged`, `\Answered`, `\Deleted`; `\Draft` — у писем в «Черновиках».
+- **Письмо целиком** (`BODY[]`) — ровно в том виде, в каком оно пришло по SMTP или через `APPEND`. Для писем, написанных в веб-почте, MIME собирается один раз и сохраняется: размер и байты не меняются между запросами.
+- Каждая команда выполняется на рабочем потоке, не на сетевом. Команды, присланные открытым текстом вместе со `STARTTLS`, не выполняются — соединение закрывается.
+- Папки — плоские (без вложенных), имена — modified UTF-7, кириллица работает.
+
 ## Веб-почта
 
 Angular 22 в стиле [synthwave-шаблона](frontend/src/assets/synthwave-design-showcase.html): стеклянные панели, неон, движущаяся сетка (выключается в настройках и при `prefers-reduced-motion`), четыре палитры и высокий контраст. Все таблицы — грид [`@jambotron/aria-grid`](https://gitea.jambotron.com/jambotron_gang/jambotron-aria-grid) (сортировка, страницы, выбор строк, массовые действия), пакет — из реестра npm Gitea (`frontend/.npmrc`).
@@ -59,12 +71,34 @@ API: `GET /api/config` (без входа), `/api/me`, `/api/me/password`, `/api
 | `MAIL_REGISTRATION` | открыть регистрацию | `false` |
 | `MAIL_CATCH_ALL` | ящик-ловушка: письма на адреса без своего ящика здесь (и на чужие домены) — сюда, наружу ничего; ящик создаётся при старте | — |
 | `SMTP_PORT` | порт SMTP | `3025` |
+| `MAIL_TLS` | TLS для SMTP: `STARTTLS` и порт `SMTPS_PORT` | `true` |
+| `MAIL_TLS_CERT`, `MAIL_TLS_KEY` | свой сертификат: PEM-цепочка и ключ (PKCS#8, `RSA PRIVATE KEY` или `EC PRIVATE KEY`); перечитывается при изменении; без них — самоподписанный | — |
+| `MAIL_TLS_DIR` | где лежит самоподписанный сертификат | `./tls` (в образе `/app/data/tls`) |
+| `SMTPS_PORT` | порт неявного TLS (465); `0` — выключен | `0` |
+| `IMAP_ENABLED`, `IMAP_PORT`, `IMAPS_PORT` | IMAP: включён; порт со STARTTLS; порт неявного TLS (`0` — выключен) | `true`, `3143`, `0` |
+| `IMAP_AUTH_WITHOUT_TLS` | вход в IMAP без TLS — **только** в закрытой сети | `false` |
 | `SMTP_AUTH_WITHOUT_TLS` | разрешить `AUTH` без шифрования — **только** в закрытой сети (docker, ВМ) | `false` |
 | `OUTBOUND_MODE` | `off` / `mx` / `smarthost` | `off` |
 | `OUTBOUND_HOST`, `OUTBOUND_PORT`, `OUTBOUND_USERNAME`, `OUTBOUND_PASSWORD`, `OUTBOUND_TLS` | smarthost (`starttls` / `ssl` / `none`) | —, `587`, —, —, `starttls` |
 | `DKIM_DOMAIN`, `DKIM_SELECTOR`, `DKIM_KEYS_DIR` | DKIM | `localhost`, `mail`, `./dkim-keys` |
 | `SPF_ENABLED`, `DMARC_ENABLED` | проверки входящих | `true` |
 | `MAIL_CORS_ORIGINS` | другие источники для веб-клиента (только разработка) | — |
+| `LOGIN_GUARD` | защита от перебора паролей (см. ниже) | `true` |
+| `LOGIN_GUARD_MAX_PER_IP`, `LOGIN_GUARD_MAX_PER_ACCOUNT` | неверных паролей за окно до блокировки: с одного IP; на один ящик с любых IP | `10`, `20` |
+| `LOGIN_GUARD_WINDOW`, `LOGIN_GUARD_BLOCK`, `LOGIN_GUARD_MAX_BLOCK` | окно подсчёта; первая блокировка; потолок (каждая следующая блокировка того же IP вдвое дольше) | `15m`, `15m`, `24h` |
+| `LOGIN_GUARD_TRUSTED_IPS` | IP через запятую, которые не блокируются по IP (ящик всё равно считается) | — |
+
+### Защита от перебора паролей
+
+Один счётчик на всё, где проверяется пароль: `AUTH` в SMTP (25/587/465), `LOGIN`/`AUTHENTICATE` в IMAP, вход в веб-почту, смена пароля.
+
+- **По IP:** 10 неверных паролей за 15 минут → IP заблокирован на 15 минут, следующая блокировка — 30 минут, потом час… до суток. Сутки тишины — счёт сначала.
+- **По ящику:** 20 неверных паролей на один ящик с разных IP (распределённый перебор) → ящик закрыт на 15 минут, **кроме** IP, с которых в него уже входили успешно (30 дней) — так перебором нельзя запереть владельца из его же почтовой программы.
+- Пока блокировка — пароль **не проверяется** вовсе: SMTP `421 4.7.0` и обрыв, IMAP `* BYE` + `NO [UNAVAILABLE]`, веб `429` с `Retry-After`. Неверный пароль отвечается через секунду; после 3 неверных в одном соединении SMTP и IMAP его закрывают.
+- «Нет такого ящика» и «неверный пароль» снаружи не отличить, оба считаются.
+- В логе: `login guard: IP … blocked for 15 min after 10 failed logins (block #1)`.
+- `X-Forwarded-For` веб-входа принимается только от прокси в частной сети (Caddy Jambotron приходит через docker/WireGuard); с публичного адреса заголовок отбрасывается — подменой IP лимит не обойти.
+- Счётчики в памяти: перезапуск их сбрасывает.
 
 ## Разработка
 
@@ -82,7 +116,7 @@ cd frontend && npm install && npx ng serve                         # http://loca
 В мастере деплоя выбрать `docker-compose.jambotron.yml`, домен дать сервису `mail`, порт `8080`.
 
 - Пароль базы и ключ токенов создаёт контейнер `secrets-init` при первом запуске (том `secrets`) — вводить ничего не нужно, в git ничего нет.
-- Ящики `admin@mail.test` (первый) и `trap@mail.test` (ловушка) создаются при старте, их пароли — в файле `/app/data/initial-passwords.txt` контейнера `mail` (том `data`, права 600): `docker exec <контейнер mail> cat /app/data/initial-passwords.txt`. Прочитать и сменить пароль в настройках.
+- Ящики `admin@mail.test` (первый) и `trap@mail.test` (ловушка) создаются при старте, их пароли печатаются в лог сервиса `mail` при первом запуске (в Jambotron: проект → Сервисы → `mail` → Логи) и лежат в файле `/app/data/initial-passwords.txt` контейнера `mail` (том `data`, права 600): `docker exec <контейнер mail> cat /app/data/initial-passwords.txt`. Прочитать и сменить пароль в настройках.
 - Регистрация открыта (`MAIL_REGISTRATION=true`): любой может завести ящик в `MAIL_DOMAINS`. Наружу письма не уходят, поэтому для тестового стенда это безопасно; закрыть — `MAIL_REGISTRATION=false`.
 - Наружу открыты только веб-почта и API. SMTP (3025) — внутри сети ВМ, наружу ничего не отправляется (`OUTBOUND_MODE=off`).
 - Домен ящиков — `MAIL_DOMAINS` (по умолчанию `mail.test`).
@@ -95,15 +129,61 @@ cd frontend && npm install && npx ng serve                         # http://loca
 
 Образ собирается из `backend/Dockerfile` в три этапа: Angular → Spring Boot (веб-клиент внутри jar) → JRE не от root.
 
+### Готовый Docker-образ
+
+Как у htop-web: Drone (`.drone.yml`) собирает `backend/Dockerfile`. На PR образ только собирается, на `master` уходит в реестр Gitea:
+
+```
+gitea.jambotron.com/jambotron_gang/reactive-mail-server:latest
+gitea.jambotron.com/jambotron_gang/reactive-mail-server:<первые 8 символов коммита master>
+```
+
+Реестр публичный: `docker pull` без логина.
+
+`docker-compose.image.yml` — тот же стенд, что `docker-compose.jambotron.yml`, но сервис `mail` берётся из образа, на ВМ ничего не собирается (деплой быстрее, Node и Gradle на ВМ не нужны). В мастере деплоя Jambotron выбрать этот файл; домен — сервису `mail`, порт `8080`. По умолчанию `latest`, он скачивается заново при каждом деплое (`pull_policy: always`); закрепить сборку — переменная `MAIL_IMAGE_TAG=<8 символов коммита>`.
+
+```bash
+docker compose -f docker-compose.image.yml up -d
+```
+
+### Настоящая почта в интернете (75.6)
+
+`docker-compose.public.yml` — приём писем для `MAIL_DOMAINS` и отправка наружу прямо на MX получателей (`OUTBOUND_MODE=mx`, порт 25), с подписью DKIM; регистрация закрыта, ловушки нет. Нужна своя ВМ с публичным адресом (Jambotron 60.8: «Публичный адрес», SMTP «да» — порт 25 по умолчанию закрыт). На этом адресе открыты:
+
+| Порт | Что |
+|---|---|
+| 25 | SMTP: письма от других серверов (STARTTLS) |
+| 587 | submission для почтовых программ (STARTTLS + вход) — тот же SMTP, что 25 |
+| 465 | SMTPS, неявный TLS |
+| 993 | IMAPS, неявный TLS |
+| 80 | только Let's Encrypt (HTTP-01), сервис `acme` |
+
+Сертификат для `MAIL_HOSTNAME` выпускает и продлевает сервис `acme` (lego, ключ EC256, продление за 30 дней, проверка дважды в сутки); хук кладёт пару в том `tls`, сервер перечитывает её сам. `mail` стартует после первого сертификата. Веб-почта (сервис `mail`, порт `8080`) — через Caddy Jambotron под **другим** именем, например `webmail.<домен>`: `MAIL_HOSTNAME` смотрит на публичный адрес ВМ, а не на Caddy.
+
+Переменные: `MAIL_DOMAINS` (например `jambocheck.com`), `MAIL_HOSTNAME` (`mail.jambocheck.com`), `ACME_EMAIL` (по умолчанию `postmaster@<домен>`).
+
+DNS до первого запуска:
+
+| Запись | Значение |
+|---|---|
+| `A mail.<домен>` | публичный адрес ВМ |
+| PTR публичного адреса | `mail.<домен>` (панель хостера, Reverse DNS) |
+| `MX <домен>` | `10 mail.<домен>` |
+| `TXT <домен>` | `v=spf1 ip4:<публичный адрес> -all` |
+| `TXT _dmarc.<домен>` | `v=DMARC1; p=none; rua=mailto:postmaster@<домен>` |
+| `TXT mail._domainkey.<домен>` | из лога `mail` при первом запуске (ключ DKIM лежит в томе `data`) |
+
+Ящик `admin@<домен>` — пароль в логе `mail` при первом запуске и в `/app/data/initial-passwords.txt`.
+
 ## Не сделано
 
-- [ ] TLS: STARTTLS для SMTP и IMAP. Пока `AUTH` — только в закрытой сети.
-- [ ] IMAP выключен: упрощённый, блокирует сетевой поток (`.block()`). Переписать и проверить с Thunderbird.
+- [ ] IMAP: проверить с Thunderbird на настоящем адресе; вложенные папки, CONDSTORE/QRESYNC, поиск по `BODY`/`TEXT` без перебора писем.
 - [ ] Пересылка не берёт вложения исходного письма — их надо прикрепить заново.
 - [ ] Встроенные картинки HTML-писем (`cid:`) показываются как вложения, а не внутри письма.
-- [ ] Защита регистрации и входа от перебора (лимит попыток, капча).
+- [x] Защита входа от перебора: SMTP, IMAP, веб (лимит по IP и по ящику, см. «Защита от перебора паролей»).
+- [ ] Защита регистрации от массового заведения ящиков (лимит, капча) — пока регистрация на публичной почте закрыта.
 - [ ] Письмо нескольким получателям: при ошибке на втором первый может получить его дважды (после повтора отправителя).
-- [ ] Своя настоящая почта: отдельная VPS, порт 25, PTR, отдельный домен (чек-лист Jambotron 75.6).
+- [ ] Настоящая почта (75.6): `docker-compose.public.yml` готов, первый запуск — `mail.jambocheck.com` на публичном адресе Horizon; адрес «прогревать» несколько недель, письма пользователям Jambotron пока через Resend (75.5).
 
 ## Лицензия
 

backend/Dockerfile

@@ -24,11 +24,11 @@ RUN chmod +x gradlew && ./gradlew :backend:bootJar --no-daemon -x test
 FROM eclipse-temurin:21-jre
 # Ubuntu image, curl included; own user: "mail" already exists (uid 8)
 RUN groupadd -r -g 10001 app && useradd -r -u 10001 -g app -d /app -s /usr/sbin/nologin app \
-    && mkdir -p /app/data/attachments /app/data/dkim-keys && chown -R app:app /app/data
+    && mkdir -p /app/data/attachments /app/data/dkim-keys /app/data/tls && chown -R app:app /app/data
 WORKDIR /app
 COPY --from=build /app/backend/build/libs/*.jar app.jar
 USER app
-ENV MAIL_ATTACHMENTS_DIR=/app/data/attachments DKIM_KEYS_DIR=/app/data/dkim-keys MAIL_PASSWORDS_FILE=/app/data/initial-passwords.txt
+ENV MAIL_ATTACHMENTS_DIR=/app/data/attachments DKIM_KEYS_DIR=/app/data/dkim-keys MAIL_PASSWORDS_FILE=/app/data/initial-passwords.txt MAIL_TLS_DIR=/app/data/tls
 EXPOSE 8080 3025
 HEALTHCHECK --interval=30s --timeout=5s --start-period=60s --retries=3 \
     CMD curl -fsS http://localhost:8080/actuator/health || exit 1

backend/src/main/java/com/mailserver/config/DataInitializer.java

@@ -28,8 +28,8 @@ import java.util.Locale;
  *   <li>the catch-all mailbox ({@code mailserver.catch-all}) if it does not exist yet — mail to unknown addresses is
  *       stored there, so it must exist.</li>
  * </ul>
- * A generated password is appended to {@code mailserver.passwords-file} (mode 600, in the data volume) — read it once
- * and change the password. Without the file setting it is printed to the log once.
+ * A generated password is printed to the log once (visible in Jambotron: project → Services → mail → Logs) and appended
+ * to {@code mailserver.passwords-file} (mode 600, in the data volume) — change it after the first login.
  */
 @Configuration
 public class DataInitializer {
@@ -63,7 +63,8 @@ public class DataInitializer {
             log.info("Mailbox created: {}", address);
         } else if (file != null) {
             appendPassword(file, address, secret);
-            log.warn("Mailbox created: {} — password in {} (change it)", address, file);
+            // also in the log: the owner sees it in Jambotron (project → Services → mail → Logs) without a shell
+            log.warn("Mailbox created: {} — password: {} (also in {}; change it)", address, secret, file);
         } else {
             log.warn("Mailbox created: {} — password: {} (shown once, change it)", address, secret);
         }

backend/src/main/java/com/mailserver/config/ImapConfig.java

@@ -0,0 +1,60 @@
+package com.mailserver.config;
+
+import com.mailserver.security.LoginGuard;
+import com.mailserver.imap.DbImapStore;
+import com.mailserver.imap.ImapServer;
+import com.mailserver.imap.ImapStore;
+import com.mailserver.repository.AttachmentRepository;
+import com.mailserver.repository.MessageRepository;
+import com.mailserver.repository.UserRepository;
+import com.mailserver.service.MailService;
+import com.mailserver.service.MessageSources;
+import com.mailserver.service.UserService;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.r2dbc.core.DatabaseClient;
+import org.springframework.util.unit.DataSize;
+
+import java.time.Duration;
+
+/** IMAP (75.2): STARTTLS on mailserver.imap.port, implicit TLS on mailserver.imaps.port when set. */
+@Configuration
+public class ImapConfig {
+
+    @Bean
+    public ImapStore imapStore(DatabaseClient db, UserRepository users, UserService userService, MailService mailService,
+                               MessageRepository messages, AttachmentRepository attachments, MessageSources sources,
+                               @Value("${mailserver.smtp.hostname:localhost}") String hostname) {
+        return new DbImapStore(db, users, userService, mailService, messages, attachments, sources, hostname);
+    }
+
+    @Bean(initMethod = "start", destroyMethod = "stop")
+    @ConditionalOnProperty(name = "mailserver.imap.enabled", havingValue = "true", matchIfMissing = true)
+    public ImapServer imapServer(ImapStore store, MailServerConfig.SmtpTlsContext tls, LoginGuard guard,
+                                 @Value("${mailserver.imap.host:0.0.0.0}") String host,
+                                 @Value("${mailserver.imap.port:3143}") int port,
+                                 @Value("${mailserver.smtp.hostname:localhost}") String hostname,
+                                 @Value("${mailserver.imap.auth-without-tls:false}") boolean authWithoutTls,
+                                 @Value("${mailserver.imap.max-literal:50MB}") DataSize maxLiteral,
+                                 @Value("${mailserver.imap.idle-timeout:30m}") Duration idleTimeout,
+                                 @Value("${mailserver.imap.idle-poll:5s}") Duration idlePoll) {
+        return new ImapServer(new ImapServer.Settings(host, port, hostname, authWithoutTls, tls.context(), false,
+                (int) maxLiteral.toBytes(), idleTimeout, idlePoll), store, guard);
+    }
+
+    @Bean(initMethod = "start", destroyMethod = "stop")
+    @ConditionalOnExpression("'${mailserver.imap.enabled:true}' == 'true' and ${mailserver.imaps.port:0} > 0 and ${mailserver.tls.enabled:true}")
+    public ImapServer imapsServer(ImapStore store, MailServerConfig.SmtpTlsContext tls, LoginGuard guard,
+                                  @Value("${mailserver.imap.host:0.0.0.0}") String host,
+                                  @Value("${mailserver.imaps.port}") int port,
+                                  @Value("${mailserver.smtp.hostname:localhost}") String hostname,
+                                  @Value("${mailserver.imap.max-literal:50MB}") DataSize maxLiteral,
+                                  @Value("${mailserver.imap.idle-timeout:30m}") Duration idleTimeout,
+                                  @Value("${mailserver.imap.idle-poll:5s}") Duration idlePoll) {
+        return new ImapServer(new ImapServer.Settings(host, port, hostname, false, tls.context(), true,
+                (int) maxLiteral.toBytes(), idleTimeout, idlePoll), store, guard);
+    }
+}

backend/src/main/java/com/mailserver/config/ImapServerConfig.java

@@ -1,580 +0,0 @@
-package com.mailserver.config;
-
-import com.mailserver.repository.FolderRepository;
-import com.mailserver.repository.MessageRepository;
-import com.mailserver.repository.UserRepository;
-import com.mailserver.service.UserService;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-import org.springframework.beans.factory.annotation.Value;
-import org.springframework.context.annotation.Configuration;
-
-import jakarta.annotation.PostConstruct;
-import jakarta.annotation.PreDestroy;
-import java.io.BufferedReader;
-import java.io.IOException;
-import java.io.InputStreamReader;
-import java.io.PrintWriter;
-import java.net.ServerSocket;
-import java.net.Socket;
-import java.nio.charset.StandardCharsets;
-import java.time.Instant;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.TimeUnit;
-
-/**
- * Встроенный IMAP-сервер для почтового сервера.
- * Поддерживает основные команды IMAP4rev1: LOGIN, SELECT, FETCH, SEARCH, STORE, EXPUNGE, LOGOUT.
- * Запускается при старте приложения и останавливается при завершении.
- */
-@Configuration
-public class ImapServerConfig {
-
-    private static final Logger log = LoggerFactory.getLogger(ImapServerConfig.class);
-
-    @Value("${mailserver.imap.enabled:true}")
-    private boolean enabled;
-
-    @Value("${mailserver.imap.port:143}")
-    private int port;
-
-    @Value("${mailserver.imap.hostname:localhost}")
-    private String hostname;
-
-    private final UserRepository userRepository;
-    private final FolderRepository folderRepository;
-    private final MessageRepository messageRepository;
-    private final UserService userService;
-
-    private ServerSocket serverSocket;
-    private ExecutorService executorService;
-
-    public ImapServerConfig(UserRepository userRepository, FolderRepository folderRepository,
-                           MessageRepository messageRepository, UserService userService) {
-        this.userRepository = userRepository;
-        this.folderRepository = folderRepository;
-        this.messageRepository = messageRepository;
-        this.userService = userService;
-    }
-
-    @PostConstruct
-    public void start() {
-        if (!enabled) {
-            log.info("IMAP-сервер отключён (mailserver.imap.enabled=false)");
-            return;
-        }
-
-        executorService = Executors.newCachedThreadPool();
-
-        try {
-            serverSocket = new ServerSocket(port);
-            log.info("IMAP-сервер запущен на порту {} (хост: {})", port, hostname);
-
-            // Принимаем подключения в цикле
-            while (!serverSocket.isClosed()) {
-                try {
-                    Socket clientSocket = serverSocket.accept();
-                    executorService.submit(() -> handleClient(clientSocket));
-                } catch (IOException e) {
-                    if (!serverSocket.isClosed()) {
-                        log.error("Ошибка при принятии подключения", e);
-                    }
-                }
-            }
-        } catch (IOException e) {
-            if (serverSocket == null || !serverSocket.isClosed()) {
-                log.error("Не удалось запустить IMAP-сервер на порту {}", port, e);
-            }
-        }
-    }
-
-    @PreDestroy
-    public void stop() {
-        log.info("Остановка IMAP-сервера...");
-        try {
-            if (serverSocket != null && !serverSocket.isClosed()) {
-                serverSocket.close();
-            }
-        } catch (IOException e) {
-            log.error("Ошибка при остановке IMAP-сервера", e);
-        }
-
-        if (executorService != null) {
-            executorService.shutdown();
-            try {
-                if (!executorService.awaitTermination(5, TimeUnit.SECONDS)) {
-                    executorService.shutdownNow();
-                }
-            } catch (InterruptedException e) {
-                executorService.shutdownNow();
-                Thread.currentThread().interrupt();
-            }
-        }
-        log.info("IMAP-сервер остановлен");
-    }
-
-    private void handleClient(Socket socket) {
-        String clientAddress = socket.getInetAddress().getHostAddress();
-        log.info("Новое IMAP-подключение от {}", clientAddress);
-
-        try (socket;
-             PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
-             BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream(), StandardCharsets.UTF_8))) {
-
-            // Отправляем приветствие
-            out.println("* OK IMAP4rev1 Server Ready");
-
-            String username = null;
-            String line;
-
-            while (username == null && (line = in.readLine()) != null) {
-                String[] parts = parseCommand(line);
-                if (parts == null) continue;
-
-                String tag = parts[0];
-                String command = parts[1].toUpperCase();
-
-                switch (command) {
-                    case "LOGIN" -> {
-                        if (parts.length >= 4) {
-                            String email = parts[2].toLowerCase();
-                            String password = parts[3];
-
-                            // Проверяем пароль через BCrypt
-                            com.mailserver.domain.User user = userRepository.findByEmail(email).block();
-                            if (user != null && userService.checkPassword(user, password)) {
-                                username = email;
-                                out.println(tag + " OK LOGIN completed");
-                                log.info("Пользователь {} успешно авторизован через IMAP", email);
-                            } else {
-                                out.println(tag + " NO LOGIN failed: invalid credentials");
-                                log.warn("Неудачная попытка IMAP-авторизации для пользователя {}", email);
-                            }
-                        } else {
-                            out.println(tag + " BAD Invalid LOGIN command");
-                        }
-                    }
-                    case "CAPABILITY" -> {
-                        out.println("* CAPABILITY IMAP4rev1 UNSELECT IDLE NAMESPACE LITERAL+");
-                        out.println(tag + " OK Capability completed");
-                    }
-                    case "LOGOUT" -> {
-                        out.println("* BYE IMAP4rev1 server terminating");
-                        out.println(tag + " OK LOGOUT completed");
-                        return;
-                    }
-                    default -> {
-                        if (username == null) {
-                            out.println(tag + " BAD Authentication required");
-                        } else {
-                            handleAuthenticatedCommand(tag, command, parts, username, out, in);
-                        }
-                    }
-                }
-            }
-        } catch (IOException e) {
-            log.error("Ошибка при обработке IMAP-подключения от {}", clientAddress, e);
-        } finally {
-            log.info("IMAP-подключение от {} закрыто", clientAddress);
-        }
-    }
-
-    private void handleAuthenticatedCommand(String tag, String command, String[] parts,
-                                           String username, PrintWriter out, BufferedReader in) {
-        switch (command) {
-            case "SELECT" -> handleSelect(tag, parts, username, out);
-            case "EXAMINE" -> handleSelect(tag, parts, username, out); // EXAMINE = SELECT в read-only режиме
-            case "FETCH" -> handleFetch(tag, parts, username, out);
-            case "SEARCH" -> handleSearch(tag, parts, username, out);
-            case "STORE" -> handleStore(tag, parts, username, out);
-            case "EXPUNGE" -> handleExpunge(tag, username, out);
-            case "LIST" -> handleList(tag, username, out);
-            case "LSUB" -> handleList(tag, username, out); // LSUB = LIST для подписок
-            case "STATUS" -> handleStatus(tag, parts, username, out);
-            case "ID" -> {
-                out.println("* ID (\"name\" \"MailServer IMAP\" \"version\" \"1.0\")");
-                out.println(tag + " OK ID completed");
-            }
-            default -> {
-                out.println(tag + " BAD Unknown command: " + command);
-            }
-        }
-    }
-
-    private void handleSelect(String tag, String[] parts, String username, PrintWriter out) {
-        if (parts.length < 3) {
-            out.println(tag + " BAD Invalid SELECT command");
-            return;
-        }
-
-        String folderName = parts[2].replace("\"", "");
-        com.mailserver.domain.User userTemp = userRepository.findByEmail(username).block();
-        if (userTemp == null) {
-            out.println(tag + " NO User not found");
-            return;
-        }
-        com.mailserver.domain.Folder folder = folderRepository.findByUserIdAndName(
-                userTemp.getId(), folderName).block();
-
-        if (folder == null) {
-            out.println(tag + " NO [NONEXISTENT] Mailbox does not exist");
-            return;
-        }
-
-        long messageCount = messageRepository.findByFolderId(folder.getId(),
-                org.springframework.data.domain.PageRequest.of(0, 1)).count().block();
-
-        out.println("* " + messageCount + " EXISTS");
-        out.println("* 0 RECENT");
-        out.println("* FLAGS (\\Answered \\Flagged \\Deleted \\Seen \\Draft)");
-        out.println(tag + " [OK] [UNSEEN 1] " + (messageCount > 0 ? "There are unseen messages in the mailbox." : "The mailbox has no unseen messages."));
-        out.println(tag + " OK [READ-WRITE] SELECT completed");
-    }
-
-    private void handleFetch(String tag, String[] parts, String username, PrintWriter out) {
-        if (parts.length < 4) {
-            out.println(tag + " BAD Invalid FETCH command");
-            return;
-        }
-
-        String messageId = parts[2];
-        String item = parts[3];
-
-        com.mailserver.domain.User user = userRepository.findByEmail(username).block();
-        if (user == null) {
-            out.println(tag + " NO User not found");
-            return;
-        }
-
-        // Получаем все сообщения пользователя
-        java.util.List<com.mailserver.domain.Folder> folders = folderRepository.findByUserId(user.getId()).collectList().block();
-        java.util.List<com.mailserver.domain.Message> allMessages = new java.util.ArrayList<>();
-        for (com.mailserver.domain.Folder folder : folders) {
-            allMessages.addAll(messageRepository.findByFolderId(folder.getId(),
-                    org.springframework.data.domain.PageRequest.of(0, 1000)).collectList().block());
-        }
-
-        // Находим сообщение по UID или индексу
-        com.mailserver.domain.Message message = null;
-        if (item.contains("UID")) {
-            // UID FETCH
-            try {
-                long uid = Long.parseLong(messageId);
-                for (com.mailserver.domain.Message msg : allMessages) {
-                    if (msg.getId().equals(uid)) {
-                        message = msg;
-                        break;
-                    }
-                }
-            } catch (NumberFormatException e) {
-                out.println(tag + " BAD Invalid UID");
-                return;
-            }
-        } else {
-            // FETCH по индексу (1-based)
-            try {
-                int index = Integer.parseInt(messageId) - 1;
-                if (index >= 0 && index < allMessages.size()) {
-                    message = allMessages.get(index);
-                }
-            } catch (NumberFormatException e) {
-                out.println(tag + " BAD Invalid message set");
-                return;
-            }
-        }
-
-        if (message == null) {
-            out.println(tag + " NO Message not found");
-            return;
-        }
-
-        // Формируем ответ FETCH
-        StringBuilder flags = new StringBuilder();
-        if (message.isRead()) flags.append("\\Seen ");
-        if (message.isFlagged()) flags.append("\\Flagged ");
-        if (message.isSpam()) flags.append("\\Deleted ");
-        if (message.getBody() != null && !message.getBody().isEmpty()) flags.append("\\Answered ");
-
-        out.println("* " + messageId + " FETCH (");
-        out.println("  UID " + message.getId());
-        out.println("  FLAGS (" + flags.toString().trim() + ")");
-        out.println("  INTERNALDATE \"" + formatImapDate(message.getReceivedAt()) + "\"");
-        out.println("  RFC822.SIZE " + (message.getMessageSize() != null ? message.getMessageSize() : 0));
-        out.println("  ENVELOPE (");
-        out.println("    \"" + escapeString(message.getReceivedAt() != null ? message.getReceivedAt().toString() : "") + "\"");
-        out.println("    \"" + escapeString(message.getSubject() != null ? message.getSubject() : "") + "\"");
-        out.println("    (\"" + escapeString(message.getSenderName() != null ? message.getSenderName() : "") + "\" 0 \"\" \"" + escapeString(message.getSenderEmail() != null ? message.getSenderEmail() : "") + "\")");
-        out.println("    (\"" + escapeString(message.getRecipientEmail() != null ? message.getRecipientEmail() : "") + "\")");
-        out.println("    (\"" + escapeString(message.getRecipientEmail() != null ? message.getRecipientEmail() : "") + "\")");
-        out.println("    (\"" + escapeString(message.getSenderEmail() != null ? message.getSenderEmail() : "") + "\")");
-        out.println("    NIL");
-        out.println("    NIL");
-        out.println("    NIL");
-        out.println("  )");
-
-        // Если запрошено тело сообщения
-        if (item.contains("BODY[]") || item.contains("RFC822")) {
-            out.println("  BODY[] {");
-            String body = message.getBody() != null ? message.getBody() : "";
-            out.println(body.length());
-            out.println(body);
-            out.println(")");
-        }
-
-        out.println(")");
-        out.println(tag + " OK FETCH completed");
-    }
-
-    private void handleSearch(String tag, String[] parts, String username, PrintWriter out) {
-        com.mailserver.domain.User user = userRepository.findByEmail(username).block();
-        if (user == null) {
-            out.println(tag + " NO User not found");
-            return;
-        }
-
-        com.mailserver.domain.Folder inbox = folderRepository.findByUserIdAndName(user.getId(), "INBOX").block();
-        if (inbox == null) {
-            out.println(tag + " OK SEARCH completed");
-            return;
-        }
-
-        // Простой поиск по ключевому слову
-        String keyword = null;
-        for (int i = 2; i < parts.length; i++) {
-            if (!parts[i].equals("ALL") && !parts[i].equals("FROM") && !parts[i].equals("SUBJECT") && !parts[i].equals("BODY")) {
-                keyword = parts[i];
-                break;
-            }
-        }
-
-        java.util.List<Long> messageIds;
-        if (keyword != null && !keyword.isEmpty()) {
-            var results = messageRepository.searchInFolder(inbox.getId(), keyword,
-                    org.springframework.data.domain.PageRequest.of(0, 100)).collectList().block();
-            messageIds = results.stream()
-                    .map(com.mailserver.domain.Message::getId)
-                    .collect(java.util.stream.Collectors.toList());
-        } else {
-            var results = messageRepository.findByFolderId(inbox.getId(),
-                    org.springframework.data.domain.PageRequest.of(0, 100)).collectList().block();
-            messageIds = results.stream()
-                    .map(com.mailserver.domain.Message::getId)
-                    .collect(java.util.stream.Collectors.toList());
-        }
-
-        StringBuilder ids = new StringBuilder();
-        for (Long id : messageIds) {
-            ids.append(id).append(" ");
-        }
-
-        out.println("* SEARCH " + ids.toString().trim());
-        out.println(tag + " OK SEARCH completed");
-    }
-
-    private void handleStore(String tag, String[] parts, String username, PrintWriter out) {
-        if (parts.length < 5) {
-            out.println(tag + " BAD Invalid STORE command");
-            return;
-        }
-
-        String messageId = parts[2];
-        String item = parts[3].toUpperCase();
-        String value = parts[4].toUpperCase();
-
-        com.mailserver.domain.User user = userRepository.findByEmail(username).block();
-        if (user == null) {
-            out.println(tag + " NO User not found");
-            return;
-        }
-
-        // Получаем все сообщения пользователя
-        java.util.List<com.mailserver.domain.Folder> folders = folderRepository.findByUserId(user.getId()).collectList().block();
-        java.util.List<com.mailserver.domain.Message> allMessages = new java.util.ArrayList<>();
-        for (com.mailserver.domain.Folder folder : folders) {
-            allMessages.addAll(messageRepository.findByFolderId(folder.getId(),
-                    org.springframework.data.domain.PageRequest.of(0, 1000)).collectList().block());
-        }
-
-        com.mailserver.domain.Message message = null;
-        try {
-            int index = Integer.parseInt(messageId) - 1;
-            if (index >= 0 && index < allMessages.size()) {
-                message = allMessages.get(index);
-            }
-        } catch (NumberFormatException e) {
-            out.println(tag + " BAD Invalid message set");
-            return;
-        }
-
-        if (message == null) {
-            out.println(tag + " NO Message not found");
-            return;
-        }
-
-        boolean saved = false;
-        if (item.contains("+FLAGS") || item.contains("FLAGS")) {
-            if (value.contains("\\SEEN")) {
-                message.setRead(true);
-                saved = true;
-            }
-            if (value.contains("\\FLAGGED")) {
-                message.setFlagged(true);
-                saved = true;
-            }
-            if (value.contains("\\DELETED")) {
-                message.setSpam(true); // Используем spam как флаг удаления для IMAP
-                saved = true;
-            }
-        }
-
-        if (item.contains("-FLAGS")) {
-            if (value.contains("\\SEEN")) {
-                message.setRead(false);
-                saved = true;
-            }
-            if (value.contains("\\FLAGGED")) {
-                message.setFlagged(false);
-                saved = true;
-            }
-        }
-
-        if (saved) {
-            messageRepository.save(message).block();
-        }
-
-        out.println("* " + messageId + " FETCH (FLAGS (" + formatFlags(message) + "))");
-        out.println(tag + " OK STORE completed");
-    }
-
-    private void handleExpunge(String tag, String username, PrintWriter out) {
-        com.mailserver.domain.User user = userRepository.findByEmail(username).block();
-        if (user == null) {
-            out.println(tag + " NO User not found");
-            return;
-        }
-
-        java.util.List<com.mailserver.domain.Folder> folders = folderRepository.findByUserId(user.getId()).collectList().block();
-        for (com.mailserver.domain.Folder folder : folders) {
-            var messages = messageRepository.findByFolderId(folder.getId(),
-                    org.springframework.data.domain.PageRequest.of(0, 1000)).collectList().block();
-            for (com.mailserver.domain.Message message : messages) {
-                if (message.isSpam()) {
-                    messageRepository.delete(message).block();
-                    folder.setMessageCount(Math.max(0, folder.getMessageCount() - 1));
-                    folderRepository.save(folder).block();
-                }
-            }
-        }
-
-        out.println("* 0 EXPUNGE");
-        out.println(tag + " OK EXPUNGE completed");
-    }
-
-    private void handleList(String tag, String username, PrintWriter out) {
-        com.mailserver.domain.User user = userRepository.findByEmail(username).block();
-        if (user == null) {
-            out.println(tag + " NO User not found");
-            return;
-        }
-
-        java.util.List<com.mailserver.domain.Folder> folders = folderRepository.findByUserId(user.getId()).collectList().block();
-        for (com.mailserver.domain.Folder folder : folders) {
-            out.println("* LIST (\\HasNoChildren) \".\" \"" + folder.getName() + "\"");
-        }
-
-        out.println(tag + " OK LIST completed");
-    }
-
-    private void handleStatus(String tag, String[] parts, String username, PrintWriter out) {
-        if (parts.length < 4) {
-            out.println(tag + " BAD Invalid STATUS command");
-            return;
-        }
-
-        String folderName = parts[2].replace("\"", "");
-        com.mailserver.domain.User user = userRepository.findByEmail(username).block();
-        if (user == null) {
-            out.println(tag + " NO User not found");
-            return;
-        }
-
-        com.mailserver.domain.Folder folder = folderRepository.findByUserIdAndName(user.getId(), folderName).block();
-        if (folder == null) {
-            out.println(tag + " NO [NONEXISTENT] Mailbox does not exist");
-            return;
-        }
-
-        long messageCount = messageRepository.findByFolderId(folder.getId(),
-                org.springframework.data.domain.PageRequest.of(0, 1)).count().block();
-        long unreadCount = messageRepository.countUnreadByFolderId(folder.getId()).block();
-
-        out.println("* STATUS " + folderName + " (MESSAGES " + messageCount + " UNSEEN " + unreadCount + " UIDNEXT " + (messageCount + 1) + " UIDVALIDITY 1)");
-        out.println(tag + " OK STATUS completed");
-    }
-
-    private String[] parseCommand(String line) {
-        if (line == null || line.trim().isEmpty()) return null;
-
-        line = line.trim();
-        int spaceIndex = line.indexOf(' ');
-        if (spaceIndex == -1) return new String[]{line, ""};
-
-        String tag = line.substring(0, spaceIndex);
-        String rest = line.substring(spaceIndex + 1).trim();
-
-        // Разбираем команду и аргументы
-        String[] parts = new String[20]; // Максимум 20 аргументов
-        parts[0] = tag;
-        int index = 1;
-
-        int i = 0;
-        while (i < rest.length() && index < parts.length) {
-            if (rest.charAt(i) == '"') {
-                // Строка в кавычках
-                int end = rest.indexOf('"', i + 1);
-                if (end == -1) break;
-                parts[index++] = rest.substring(i + 1, end);
-                i = end + 1;
-            } else if (Character.isWhitespace(rest.charAt(i))) {
-                i++;
-            } else {
-                int end = rest.indexOf(' ', i);
-                if (end == -1) end = rest.length();
-                parts[index++] = rest.substring(i, end);
-                i = end;
-            }
-        }
-
-        // Обрезаем массив до нужного размера
-        String[] result = new String[index];
-        System.arraycopy(parts, 0, result, 0, index);
-        return result;
-    }
-
-    private String formatImapDate(Instant instant) {
-        if (instant == null) return "";
-        // Формат IMAP: "dd-MMM-yyyy hh:mm:ss +0000"
-        String[] months = {"Jan", "Feb", "Mar", "Apr", "May", "Jun",
-                           "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
-        java.time.LocalDate date = instant.atZone(java.time.ZoneOffset.UTC).toLocalDate();
-        java.time.LocalTime time = instant.atZone(java.time.ZoneOffset.UTC).toLocalTime();
-
-        return String.format("%02d-%s-%04d %02d:%02d:%02d +0000",
-                date.getDayOfMonth(), months[date.getMonthValue() - 1], date.getYear(),
-                time.getHour(), time.getMinute(), time.getSecond());
-    }
-
-    private String escapeString(String str) {
-        if (str == null) return "";
-        return str.replace("\\", "\\\\").replace("\"", "\\\"");
-    }
-
-    private String formatFlags(com.mailserver.domain.Message message) {
-        StringBuilder flags = new StringBuilder();
-        if (message.isRead()) flags.append("\\Seen ");
-        if (message.isFlagged()) flags.append("\\Flagged ");
-        if (message.isSpam()) flags.append("\\Deleted ");
-        return flags.toString().trim();
-    }
-}

backend/src/main/java/com/mailserver/config/LoginGuardConfig.java

@@ -0,0 +1,74 @@
+package com.mailserver.config;
+
+import com.mailserver.security.LoginGuard;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.web.server.adapter.ForwardedHeaderTransformer;
+
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+/** Brute-force protection (one guard for SMTP, IMAP and the web) and whose X-Forwarded-* headers to believe. */
+@Configuration
+public class LoginGuardConfig {
+
+    @Bean
+    public LoginGuard loginGuard(@Value("${mailserver.login-guard.enabled:true}") boolean enabled,
+                                 @Value("${mailserver.login-guard.max-per-ip:10}") int maxPerIp,
+                                 @Value("${mailserver.login-guard.max-per-account:20}") int maxPerAccount,
+                                 @Value("${mailserver.login-guard.window:15m}") Duration window,
+                                 @Value("${mailserver.login-guard.block:15m}") Duration block,
+                                 @Value("${mailserver.login-guard.max-block:24h}") Duration maxBlock,
+                                 @Value("${mailserver.login-guard.known-ip-ttl:30d}") Duration knownIpTtl,
+                                 @Value("${mailserver.login-guard.trusted-ips:}") String trustedIps,
+                                 @Value("${mailserver.login-guard.failure-delay:1s}") Duration failureDelay) {
+        Set<String> trusted = Arrays.stream(trustedIps.split(","))
+                .map(String::trim).filter(s -> !s.isEmpty()).collect(Collectors.toUnmodifiableSet());
+        return new LoginGuard(new LoginGuard.Settings(enabled, maxPerIp, maxPerAccount, window, block, maxBlock,
+                knownIpTtl, trusted, failureDelay));
+    }
+
+    /**
+     * Replaces Boot's transformer (server.forward-headers-strategy=framework): X-Forwarded-* / Forwarded are believed
+     * only from a proxy in a private network (Jambotron's Caddy comes over the docker network / WireGuard). A request
+     * straight from the internet (the VM's public address) has them removed — otherwise anyone could put a new
+     * X-Forwarded-For into every login attempt and never hit the per-IP limit.
+     */
+    @Bean(name = "forwardedHeaderTransformer")
+    public ForwardedHeaderTransformer forwardedHeaderTransformer() {
+        return new TrustedProxyHeaderTransformer();
+    }
+
+    static final class TrustedProxyHeaderTransformer extends ForwardedHeaderTransformer {
+
+        private final ForwardedHeaderTransformer stripOnly = new ForwardedHeaderTransformer();
+
+        TrustedProxyHeaderTransformer() {
+            stripOnly.setRemoveOnly(true);
+        }
+
+        @Override
+        public ServerHttpRequest apply(ServerHttpRequest request) {
+            return privatePeer(request.getRemoteAddress()) ? super.apply(request) : stripOnly.apply(request);
+        }
+    }
+
+    /** Loopback, 10/8, 172.16/12, 192.168/16, link-local, IPv6 fc00::/7. */
+    static boolean privatePeer(InetSocketAddress peer) {
+        if (peer == null || peer.getAddress() == null) {
+            return false;
+        }
+        InetAddress a = peer.getAddress();
+        if (a.isLoopbackAddress() || a.isSiteLocalAddress() || a.isLinkLocalAddress()) {
+            return true;
+        }
+        byte[] b = a.getAddress();
+        return b.length == 16 && (b[0] & 0xfe) == 0xfc;
+    }
+}

backend/src/main/java/com/mailserver/config/MailServerConfig.java

@@ -1,14 +1,19 @@
 package com.mailserver.config;
 
+import com.mailserver.security.LoginGuard;
 import com.mailserver.delivery.SmtpDeliveryClient;
 import com.mailserver.smtp.MailRouter;
 import com.mailserver.smtp.SmtpServer;
+import com.mailserver.smtp.SmtpTls;
+import io.netty.handler.ssl.SslContext;
 import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.scheduling.annotation.EnableScheduling;
 
+import java.nio.file.Path;
 import java.time.Duration;
 import java.util.Locale;
 
@@ -17,16 +22,46 @@ import java.util.Locale;
 @EnableScheduling
 public class MailServerConfig {
 
+    /**
+     * Certificate for SMTP TLS: mailserver.tls.cert-file + key-file (PEM), or a self-signed one in mailserver.tls.dir.
+     * mailserver.tls.enabled=false — no TLS at all.
+     */
+    @Bean
+    public SmtpTlsContext smtpTlsContext(@Value("${mailserver.tls.enabled:true}") boolean enabled,
+                                         @Value("${mailserver.tls.cert-file:}") String certFile,
+                                         @Value("${mailserver.tls.key-file:}") String keyFile,
+                                         @Value("${mailserver.tls.dir:./tls}") String dir,
+                                         @Value("${mailserver.smtp.hostname:localhost}") String hostname) throws Exception {
+        return new SmtpTlsContext(enabled ? SmtpTls.serverContext(certFile, keyFile, Path.of(dir), hostname) : null);
+    }
+
+    public record SmtpTlsContext(SslContext context) {
+    }
+
     @Bean(initMethod = "start", destroyMethod = "stop")
     @ConditionalOnProperty(name = "mailserver.smtp.enabled", havingValue = "true", matchIfMissing = true)
-    public SmtpServer smtpServer(MailRouter router,
+    public SmtpServer smtpServer(MailRouter router, SmtpTlsContext tls, LoginGuard guard,
                                  @Value("${mailserver.smtp.host:0.0.0.0}") String host,
                                  @Value("${mailserver.smtp.port:3025}") int port,
                                  @Value("${mailserver.smtp.hostname:localhost}") String hostname,
                                  @Value("${mailserver.smtp.max-message-bytes:26214400}") long maxBytes,
                                  @Value("${mailserver.smtp.auth-without-tls:false}") boolean authWithoutTls,
                                  @Value("${mailserver.smtp.idle-timeout:5m}") Duration idleTimeout) {
-        return new SmtpServer(new SmtpServer.Settings(host, port, hostname, maxBytes, authWithoutTls, idleTimeout), router);
+        return new SmtpServer(new SmtpServer.Settings(host, port, hostname, maxBytes, authWithoutTls, idleTimeout,
+                tls.context(), false), router, guard);
+    }
+
+    /** Implicit TLS (RFC 8314, usually port 465) — only when mailserver.smtps.port is set and TLS is on. */
+    @Bean(initMethod = "start", destroyMethod = "stop")
+    @ConditionalOnExpression("${mailserver.smtps.port:0} > 0 and ${mailserver.tls.enabled:true}")
+    public SmtpServer smtpsServer(MailRouter router, SmtpTlsContext tls, LoginGuard guard,
+                                  @Value("${mailserver.smtp.host:0.0.0.0}") String host,
+                                  @Value("${mailserver.smtps.port}") int port,
+                                  @Value("${mailserver.smtp.hostname:localhost}") String hostname,
+                                  @Value("${mailserver.smtp.max-message-bytes:26214400}") long maxBytes,
+                                  @Value("${mailserver.smtp.idle-timeout:5m}") Duration idleTimeout) {
+        return new SmtpServer(new SmtpServer.Settings(host, port, hostname, maxBytes, false, idleTimeout,
+                tls.context(), true), router, guard);
     }
 
     /**

backend/src/main/java/com/mailserver/controller/AuthenticationController.java

@@ -10,11 +10,16 @@ import com.mailserver.dto.ProfileUpdateRequest;
 import com.mailserver.dto.RegisterRequest;
 import com.mailserver.service.MailService;
 import com.mailserver.service.UserService;
+import com.mailserver.security.LoginGuard;
 import com.mailserver.util.JwtUtils;
 import jakarta.validation.Valid;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Value;
+import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
+import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.security.core.Authentication;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PostMapping;
@@ -25,6 +30,8 @@ import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.server.ResponseStatusException;
 import reactor.core.publisher.Mono;
 
+import java.net.InetSocketAddress;
+import java.time.Duration;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
@@ -34,6 +41,10 @@ import java.util.Set;
 @RequestMapping("/api")
 public class AuthenticationController {
 
+    private static final Logger log = LoggerFactory.getLogger(AuthenticationController.class);
+    /** Marker for "no such mailbox or wrong password": both look the same from outside. */
+    private static final User NO_USER = new User();
+
     /** Service addresses nobody can register (RFC 2142 and ours). */
     static final Set<String> RESERVED = Set.of("postmaster", "abuse", "mailer-daemon", "hostmaster", "webmaster",
             "root", "admin", "noreply", "no-reply", "security", "support");
@@ -43,9 +54,12 @@ public class AuthenticationController {
     private final JwtUtils jwtUtils;
     private final MailDomains domains;
     private final boolean registrationEnabled;
+    private final LoginGuard guard;
 
     public AuthenticationController(UserService userService, MailService mailService, JwtUtils jwtUtils, MailDomains domains,
-                                    @Value("${mailserver.registration.enabled:false}") boolean registrationEnabled) {
+                                    @Value("${mailserver.registration.enabled:false}") boolean registrationEnabled,
+                                    LoginGuard guard) {
+        this.guard = guard;
         this.userService = userService;
         this.mailService = mailService;
         this.jwtUtils = jwtUtils;
@@ -60,23 +74,34 @@ public class AuthenticationController {
     }
 
     @PostMapping("/login")
-    public Mono<ResponseEntity<?>> login(@Valid @RequestBody Mono<LoginRequest> requestMono) {
-        return requestMono.flatMap(request ->
-            userService.findByEmail(request.getEmail().trim().toLowerCase(Locale.ROOT))
-                .switchIfEmpty(Mono.error(new IllegalArgumentException("Invalid credentials")))
+    public Mono<ResponseEntity<?>> login(@Valid @RequestBody Mono<LoginRequest> requestMono, ServerHttpRequest http) {
+        String ip = clientIp(http);
+        return requestMono.flatMap(request -> {
+            String email = request.getEmail().trim().toLowerCase(Locale.ROOT);
+            Duration wait = guard.retryAfter(ip, email);
+            if (!wait.isZero()) {
+                log.warn("WEB {}: login as {} refused, blocked for {}", ip, email, LoginGuard.human(wait));
+                return Mono.just(tooMany(wait));
+            }
+            return userService.findByEmail(email)
+                .map(user -> userService.checkPassword(user, request.getPassword()) ? user : NO_USER)
+                .onErrorResume(IllegalArgumentException.class, e -> Mono.just(NO_USER))
+                .defaultIfEmpty(NO_USER)
                 .flatMap(user -> {
+                    if (user == NO_USER) {
+                        guard.failure(ip, email);
+                        log.warn("WEB {}: authentication failed for {}", ip, email);
+                        Mono<ResponseEntity<?>> answer = Mono.just(ResponseEntity.badRequest().body(Map.of("error", "Invalid credentials")));
+                        Duration delay = guard.failureDelay();
+                        return delay.isZero() ? answer : answer.delayElement(delay);
+                    }
+                    guard.success(ip, email);
                     if (!user.isActive()) {
                         return Mono.just(ResponseEntity.badRequest().body(Map.of("error", "User is deactivated")));
                     }
-                    if (!userService.checkPassword(user, request.getPassword())) {
-                        return Mono.just(ResponseEntity.badRequest().body(Map.of("error", "Invalid credentials")));
-                    }
                     return Mono.just(ResponseEntity.ok(token(user)));
-                })
-                .onErrorResume(IllegalArgumentException.class, e ->
-                    Mono.just(ResponseEntity.badRequest().body(Map.of("error", "Invalid credentials")))
-                )
-        );
+                });
+        });
     }
 
     /** New mailbox in one of our domains; logs in right away (the answer carries the token). */
@@ -116,12 +141,41 @@ public class AuthenticationController {
     }
 
     @PutMapping("/me/password")
-    public Mono<Map<String, String>> changePassword(Mono<Authentication> auth, @Valid @RequestBody Mono<PasswordChangeRequest> body) {
+    public Mono<Map<String, String>> changePassword(Mono<Authentication> auth, @Valid @RequestBody Mono<PasswordChangeRequest> body,
+                                                    ServerHttpRequest http) {
+        String ip = clientIp(http);
         return user(auth).zipWith(body)
-                .flatMap(pair -> userService.changePassword(pair.getT1(), pair.getT2().currentPassword(), pair.getT2().newPassword()))
+                .flatMap(pair -> {
+                    User user = pair.getT1();
+                    // Someone with a stolen session must not guess the current password either
+                    Duration wait = guard.retryAfter(ip, user.getEmail());
+                    if (!wait.isZero()) {
+                        return Mono.error(new ResponseStatusException(HttpStatus.TOO_MANY_REQUESTS,
+                                "Too many failed attempts, try again in " + LoginGuard.human(wait)));
+                    }
+                    if (!userService.checkPassword(user, pair.getT2().currentPassword())) {
+                        guard.failure(ip, user.getEmail());
+                    }
+                    return userService.changePassword(user, pair.getT2().currentPassword(), pair.getT2().newPassword());
+                })
                 .thenReturn(Map.of("message", "Password changed"));
     }
 
+    private static ResponseEntity<?> tooMany(Duration wait) {
+        return ResponseEntity.status(HttpStatus.TOO_MANY_REQUESTS)
+                .header(HttpHeaders.RETRY_AFTER, String.valueOf(Math.max(1, (wait.toMillis() + 999) / 1000)))
+                .body(Map.of("error", "Too many failed logins, try again in " + LoginGuard.human(wait)));
+    }
+
+    /** Client address; behind Caddy it comes from X-Forwarded-For (server.forward-headers-strategy=framework). */
+    static String clientIp(ServerHttpRequest http) {
+        InetSocketAddress address = http.getRemoteAddress();
+        if (address == null) {
+            return "unknown";
+        }
+        return address.getAddress() != null ? address.getAddress().getHostAddress() : address.getHostString();
+    }
+
     private Mono<ProfileResponse> profile(User user) {
         return mailService.usedBytes(user.getId())
                 .map(used -> new ProfileResponse(user.getEmail(), user.getDisplayName(), used,

backend/src/main/java/com/mailserver/imap/DbImapStore.java

@@ -0,0 +1,285 @@
+package com.mailserver.imap;
+
+import com.mailserver.domain.Attachment;
+import com.mailserver.domain.Message;
+import com.mailserver.domain.User;
+import com.mailserver.repository.AttachmentRepository;
+import com.mailserver.repository.MessageRepository;
+import com.mailserver.repository.UserRepository;
+import com.mailserver.service.LocalDelivery;
+import com.mailserver.service.MailService;
+import com.mailserver.service.MessageSources;
+import com.mailserver.service.UserService;
+import jakarta.mail.Session;
+import jakarta.mail.internet.InternetAddress;
+import jakarta.mail.internet.MimeMessage;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.r2dbc.core.DatabaseClient;
+import org.springframework.web.server.ResponseStatusException;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Locale;
+import java.util.Properties;
+import java.util.UUID;
+
+/** {@link ImapStore} over the mail server's PostgreSQL tables (the same data the web client shows). */
+public class DbImapStore implements ImapStore {
+
+    private static final Logger log = LoggerFactory.getLogger(DbImapStore.class);
+
+    private final DatabaseClient db;
+    private final UserRepository users;
+    private final UserService userService;
+    private final MailService mailService;
+    private final MessageRepository messages;
+    private final AttachmentRepository attachments;
+    private final MessageSources sources;
+    private final String hostname;
+
+    public DbImapStore(DatabaseClient db, UserRepository users, UserService userService, MailService mailService,
+                       MessageRepository messages, AttachmentRepository attachments, MessageSources sources,
+                       String hostname) {
+        this.db = db;
+        this.users = users;
+        this.userService = userService;
+        this.mailService = mailService;
+        this.messages = messages;
+        this.attachments = attachments;
+        this.sources = sources;
+        this.hostname = hostname;
+    }
+
+    @Override
+    public Account authenticate(String username, String password) {
+        User user = users.findByEmail(username.trim().toLowerCase(Locale.ROOT)).block();
+        if (user == null || !user.isActive() || !userService.checkPassword(user, password)) {
+            return null;
+        }
+        return new Account(user.getId(), user.getEmail());
+    }
+
+    @Override
+    public List<Mailbox> mailboxes(long userId) {
+        return db.sql("SELECT id, name, is_system, uid_validity, uid_next FROM folders WHERE user_id = :u ORDER BY id")
+                .bind("u", userId)
+                .map(row -> new Mailbox(row.get("id", Long.class), row.get("name", String.class),
+                        Boolean.TRUE.equals(row.get("is_system", Boolean.class)),
+                        row.get("uid_validity", Long.class), row.get("uid_next", Long.class)))
+                .all().collectList().block();
+    }
+
+    @Override
+    public Mailbox create(long userId, String name) {
+        try {
+            var created = mailService.createFolder(userId, name).block();
+            return mailboxes(userId).stream().filter(m -> m.id() == created.id()).findFirst().orElseThrow();
+        } catch (ResponseStatusException e) {
+            throw new Refused(e.getReason());
+        }
+    }
+
+    @Override
+    public void rename(long userId, Mailbox mailbox, String newName) {
+        try {
+            mailService.renameFolder(mailbox.id(), userId, newName).block();
+        } catch (ResponseStatusException e) {
+            throw new Refused(e.getReason());
+        }
+    }
+
+    @Override
+    public void delete(long userId, Mailbox mailbox) {
+        try {
+            mailService.deleteFolder(mailbox.id(), userId).block();
+        } catch (ResponseStatusException e) {
+            throw new Refused(e.getReason());
+        }
+    }
+
+    @Override
+    public List<Entry> entries(long folderId) {
+        return db.sql("SELECT id, uid, is_read, is_flagged, is_answered, is_deleted, received_at FROM messages "
+                        + "WHERE folder_id = :f ORDER BY uid")
+                .bind("f", folderId)
+                .map(row -> new Entry(row.get("id", Long.class), row.get("uid", Long.class),
+                        Boolean.TRUE.equals(row.get("is_read", Boolean.class)),
+                        Boolean.TRUE.equals(row.get("is_flagged", Boolean.class)),
+                        Boolean.TRUE.equals(row.get("is_answered", Boolean.class)),
+                        Boolean.TRUE.equals(row.get("is_deleted", Boolean.class)),
+                        instant(row.get("received_at"))))
+                .all().collectList().block();
+    }
+
+    @Override
+    public byte[] source(long messageId) {
+        byte[] raw = sources.get(messageId).block();
+        if (raw != null) {
+            return raw;
+        }
+        Message message = messages.findById(messageId).block();
+        if (message == null) {
+            return new byte[0];
+        }
+        try {
+            List<Attachment> files = attachments.findByMessageId(messageId).collectList().block();
+            raw = MimeSource.build(message, files, hostname);
+        } catch (Exception e) {
+            log.warn("IMAP: cannot build message {}: {}", messageId, e.toString());
+            return ("Subject: " + message.getSubject() + "\r\n\r\n" + message.getBody()).getBytes();
+        }
+        sources.put(messageId, raw).block();
+        return raw;
+    }
+
+    @Override
+    public void setFlags(long messageId, boolean seen, boolean flagged, boolean answered, boolean deleted) {
+        db.sql("UPDATE messages SET is_read = :s, is_flagged = :f, is_answered = :a, is_deleted = :d WHERE id = :id")
+                .bind("s", seen).bind("f", flagged).bind("a", answered).bind("d", deleted).bind("id", messageId)
+                .then().block();
+    }
+
+    @Override
+    public long append(long userId, Mailbox target, byte[] raw, boolean seen, boolean flagged, boolean answered,
+                       boolean deleted, Instant internalDate) {
+        try {
+            MimeMessage mime = new MimeMessage(Session.getInstance(new Properties()), new ByteArrayInputStream(raw));
+            Message message = new Message();
+            message.setFolderId(target.id());
+            String senderEmail = "unknown@" + hostname;
+            String senderName = null;
+            if (mime.getFrom() != null && mime.getFrom().length > 0 && mime.getFrom()[0] instanceof InternetAddress from) {
+                senderEmail = from.getAddress();
+                senderName = from.getPersonal();
+            }
+            message.setSenderEmail(senderEmail);
+            message.setSenderName(senderName);
+            String to = LocalDelivery.addresses(mime, jakarta.mail.Message.RecipientType.TO);
+            message.setRecipientEmail(to == null ? "" : to);
+            message.setCcEmail(LocalDelivery.addresses(mime, jakarta.mail.Message.RecipientType.CC));
+            message.setSubject(mime.getSubject() == null ? "" : mime.getSubject());
+            LocalDelivery.Body body = LocalDelivery.body(mime);
+            message.setBody(body.text());
+            message.setHtml(body.html());
+            message.setRead(seen);
+            message.setFlagged(flagged);
+            message.setSpam(target.system() && "Spam".equals(target.name()));
+            message.setReceivedAt(internalDate == null ? Instant.now() : internalDate);
+            String messageId = mime.getMessageID();
+            message.setMessageId(messageId == null ? UUID.randomUUID().toString() : messageId.replaceAll("^<|>$", ""));
+            message.setMessageSize((long) raw.length);
+            Message stored = messages.save(message).block();
+            for (LocalDelivery.FilePart file : LocalDelivery.attachments(mime)) {
+                mailService.storeIncomingAttachment(stored.getId(), file.name(), file.contentType(), file.bytes());
+            }
+            sources.put(stored.getId(), raw).block();
+            setFlags(stored.getId(), seen, flagged, answered, deleted);
+            return uid(stored.getId());
+        } catch (Refused e) {
+            throw e;
+        } catch (Exception e) {
+            log.warn("IMAP APPEND to {} failed: {}", target.name(), e.toString());
+            throw new Refused("Cannot store the message: " + e.getMessage());
+        }
+    }
+
+    @Override
+    public List<Long> copy(long userId, List<Entry> list, Mailbox target) {
+        boolean spam = target.system() && "Spam".equals(target.name());
+        List<Long> uids = new ArrayList<>();
+        for (Entry entry : list) {
+            Long newId = db.sql("INSERT INTO messages (folder_id, sender_email, sender_name, recipient_email, cc_email, "
+                            + "subject, body, is_html, is_read, is_flagged, is_spam, is_answered, is_deleted, message_size, "
+                            + "received_at, message_id) "
+                            + "SELECT :t, sender_email, sender_name, recipient_email, cc_email, subject, body, is_html, "
+                            + "is_read, is_flagged, :spam, is_answered, is_deleted, message_size, received_at, message_id "
+                            + "FROM messages WHERE id = :id RETURNING id")
+                    .bind("t", target.id()).bind("spam", spam).bind("id", entry.id())
+                    .map(row -> row.get("id", Long.class)).one().block();
+            if (newId == null) {
+                continue;
+            }
+            for (Attachment attachment : attachments.findByMessageId(entry.id()).collectList().block()) {
+                copyAttachment(attachment, newId);
+            }
+            db.sql("INSERT INTO message_sources (message_id, raw) SELECT :n, raw FROM message_sources WHERE message_id = :o")
+                    .bind("n", newId).bind("o", entry.id()).then().block();
+            uids.add(uid(newId));
+        }
+        return uids;
+    }
+
+    private void copyAttachment(Attachment attachment, long newMessageId) {
+        try {
+            Path from = Paths.get(attachment.getFilePath());
+            Path to = from.resolveSibling(UUID.randomUUID() + "_" + from.getFileName().toString().replaceFirst("^[0-9a-f-]{36}_", ""));
+            Files.copy(from, to);
+            Attachment copy = new Attachment();
+            copy.setMessageId(newMessageId);
+            copy.setFilename(attachment.getFilename());
+            copy.setContentType(attachment.getContentType());
+            copy.setSizeBytes(attachment.getSizeBytes());
+            copy.setFilePath(to.toString());
+            copy.setContentId(attachment.getContentId());
+            attachments.save(copy).block();
+        } catch (IOException e) {
+            log.warn("IMAP COPY: attachment {} not copied: {}", attachment.getFilePath(), e.toString());
+        }
+    }
+
+    @Override
+    public List<Long> move(long userId, List<Entry> list, Mailbox target) {
+        boolean spam = target.system() && "Spam".equals(target.name());
+        List<Long> uids = new ArrayList<>();
+        for (Entry entry : list) {
+            Long uid = db.sql("UPDATE messages SET folder_id = :t, is_spam = :spam WHERE id = :id RETURNING uid")
+                    .bind("t", target.id()).bind("spam", spam).bind("id", entry.id())
+                    .map(row -> row.get("uid", Long.class)).one().block();
+            if (uid != null) {
+                uids.add(uid);
+            }
+        }
+        return uids;
+    }
+
+    @Override
+    public void expunge(List<Long> messageIds) {
+        for (Long id : messageIds) {
+            for (Attachment attachment : attachments.findByMessageId(id).collectList().block()) {
+                try {
+                    Files.deleteIfExists(Paths.get(attachment.getFilePath()));
+                } catch (IOException e) {
+                    log.warn("Attachment file {} not deleted: {}", attachment.getFilePath(), e.getMessage());
+                }
+            }
+            messages.deleteById(id).block();
+        }
+    }
+
+    private long uid(long messageId) {
+        return db.sql("SELECT uid FROM messages WHERE id = :id").bind("id", messageId)
+                .map(row -> row.get("uid", Long.class)).one().block();
+    }
+
+    private static Instant instant(Object value) {
+        if (value instanceof Instant instant) {
+            return instant;
+        }
+        if (value instanceof LocalDateTime local) {
+            return local.toInstant(ZoneOffset.UTC);
+        }
+        if (value instanceof java.time.OffsetDateTime offset) {
+            return offset.toInstant();
+        }
+        return Instant.EPOCH;
+    }
+}

backend/src/main/java/com/mailserver/imap/ImapReader.java

@@ -0,0 +1,194 @@
+package com.mailserver.imap;
+
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Reads one IMAP command: the decoder has already collected it whole, with its literals inline
+ * ("{n}\r\n" + n bytes, or "{n+}\r\n" + n bytes).
+ */
+final class ImapReader {
+
+    static final class SyntaxError extends RuntimeException {
+        SyntaxError(String message) {
+            super(message);
+        }
+    }
+
+    private final byte[] b;
+    private int pos;
+
+    ImapReader(byte[] command) {
+        this(command, true);
+    }
+
+    private ImapReader(byte[] command, boolean stripLineEnd) {
+        int end = command.length;
+        if (!stripLineEnd) {
+            this.b = command;
+            return;
+        }
+        if (end > 0 && command[end - 1] == '\n') {
+            end--;
+        }
+        if (end > 0 && command[end - 1] == '\r') {
+            end--;
+        }
+        this.b = java.util.Arrays.copyOf(command, end);
+    }
+
+    boolean atEnd() {
+        return pos >= b.length;
+    }
+
+    int peek() {
+        return pos < b.length ? b[pos] & 0xff : -1;
+    }
+
+    void sp() {
+        if (peek() != ' ') {
+            throw new SyntaxError("Expected a space");
+        }
+        while (peek() == ' ') {
+            pos++;
+        }
+    }
+
+    boolean optionalSp() {
+        if (peek() == ' ') {
+            sp();
+            return true;
+        }
+        return false;
+    }
+
+    void expect(char c) {
+        if (peek() != c) {
+            throw new SyntaxError("Expected '" + c + "'");
+        }
+        pos++;
+    }
+
+    /** Characters up to a space, parenthesis, or the end (an atom; also tags, sequence sets, flags). */
+    String atom() {
+        int start = pos;
+        while (pos < b.length) {
+            int c = b[pos] & 0xff;
+            if (c == ' ' || c == '(' || c == ')' || c == '{' || c == '"' || c < 0x20 || c == 0x7f) {
+                break;
+            }
+            pos++;
+        }
+        if (pos == start) {
+            throw new SyntaxError("Expected an atom");
+        }
+        return new String(b, start, pos - start, StandardCharsets.UTF_8);
+    }
+
+    /** Atom, quoted string or literal. */
+    String astring() {
+        int c = peek();
+        if (c == '"' || c == '{') {
+            return new String(stringBytes(), StandardCharsets.UTF_8);
+        }
+        return atom();
+    }
+
+    /** Quoted string or literal, raw bytes. */
+    byte[] stringBytes() {
+        int c = peek();
+        if (c == '"') {
+            pos++;
+            java.io.ByteArrayOutputStream out = new java.io.ByteArrayOutputStream();
+            while (true) {
+                if (pos >= b.length) {
+                    throw new SyntaxError("Unterminated quoted string");
+                }
+                byte x = b[pos++];
+                if (x == '"') {
+                    return out.toByteArray();
+                }
+                if (x == '\\' && pos < b.length) {
+                    x = b[pos++];
+                }
+                out.write(x);
+            }
+        }
+        if (c == '{') {
+            int close = indexOf('}', pos);
+            if (close < 0) {
+                throw new SyntaxError("Bad literal");
+            }
+            String size = new String(b, pos + 1, close - pos - 1, StandardCharsets.US_ASCII);
+            if (size.endsWith("+")) {
+                size = size.substring(0, size.length() - 1);
+            }
+            int length;
+            try {
+                length = Integer.parseInt(size);
+            } catch (NumberFormatException e) {
+                throw new SyntaxError("Bad literal size");
+            }
+            pos = close + 1;
+            if (peek() == '\r') {
+                pos++;
+            }
+            expect('\n');
+            if (pos + length > b.length) {
+                throw new SyntaxError("Literal shorter than announced");
+            }
+            byte[] data = java.util.Arrays.copyOfRange(b, pos, pos + length);
+            pos += length;
+            return data;
+        }
+        throw new SyntaxError("Expected a string");
+    }
+
+    /** "(a b c)" → [a, b, c] (atoms or strings); an atom without parentheses → [atom]. */
+    List<String> list() {
+        List<String> items = new ArrayList<>();
+        if (peek() != '(') {
+            items.add(astring());
+            return items;
+        }
+        pos++;
+        while (peek() == ' ') {
+            pos++;
+        }
+        while (peek() != ')') {
+            if (atEnd()) {
+                throw new SyntaxError("Unterminated list");
+            }
+            items.add(astring());
+            while (peek() == ' ') {
+                pos++;
+            }
+        }
+        pos++;
+        return items;
+    }
+
+    /** Everything left, as text (used for FETCH attributes and SEARCH keys parsed by their own readers). */
+    String rest() {
+        String text = new String(b, pos, b.length - pos, StandardCharsets.UTF_8);
+        pos = b.length;
+        return text;
+    }
+
+    /** A reader over the rest, as is (SEARCH may hold literals). */
+    ImapReader restReader() {
+        ImapReader reader = new ImapReader(java.util.Arrays.copyOfRange(b, pos, b.length), false);
+        pos = b.length;
+        return reader;
+    }
+
+    private int indexOf(char c, int from) {
+        for (int i = from; i < b.length; i++) {
+            if (b[i] == c) {
+                return i;
+            }
+        }
+        return -1;
+    }
+}

backend/src/main/java/com/mailserver/imap/ImapServer.java

@@ -0,0 +1,273 @@
+package com.mailserver.imap;
+
+import com.mailserver.security.LoginGuard;
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelPipeline;
+import io.netty.handler.codec.ByteToMessageDecoder;
+import io.netty.handler.codec.TooLongFrameException;
+import io.netty.handler.ssl.SslContext;
+import io.netty.handler.ssl.SslHandler;
+import io.netty.handler.timeout.ReadTimeoutHandler;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+import reactor.core.publisher.Sinks;
+import reactor.core.scheduler.Schedulers;
+import reactor.netty.Connection;
+import reactor.netty.DisposableServer;
+import reactor.netty.NettyOutbound;
+import reactor.netty.tcp.TcpServer;
+
+import java.io.ByteArrayOutputStream;
+import java.net.InetSocketAddress;
+import java.nio.charset.StandardCharsets;
+import java.time.Duration;
+import java.util.List;
+import java.util.Locale;
+import java.util.concurrent.TimeUnit;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * IMAP server (RFC 3501) on Reactor Netty.
+ * <ul>
+ *   <li>{@link CommandDecoder} collects whole commands with their literals ({n} — after "+ Ready", {n+} — at once);</li>
+ *   <li>each command runs on a worker thread (database, MIME parsing), never on the event loop; responses are written
+ *       in order, one command at a time;</li>
+ *   <li>TLS: STARTTLS, or implicit TLS on a separate port (993); LOGIN/AUTHENTICATE only inside TLS unless
+ *       {@code authWithoutTls}; plain text sent together with STARTTLS is never executed;</li>
+ *   <li>IDLE: changes of the selected mailbox are pushed every {@code idlePoll} until DONE.</li>
+ * </ul>
+ */
+public class ImapServer {
+
+    private static final Logger log = LoggerFactory.getLogger(ImapServer.class);
+
+    static final int MAX_LINE = 64 * 1024;
+    private static final int MAX_QUEUED = 1000;
+    private static final Pattern LITERAL = Pattern.compile("\\{(\\d+)(\\+?)}\r?\n$");
+    private static final Pattern IDLE = Pattern.compile("^(\\S+) IDLE\\s*$", Pattern.CASE_INSENSITIVE);
+    private static final Duration IDLE_MAX = Duration.ofMinutes(29);
+
+    /**
+     * @param tls            certificate; null — no TLS
+     * @param implicitTls    TLS from the first byte (port 993)
+     * @param maxLiteral     the largest literal accepted (APPEND of a big message)
+     * @param idlePoll       how often IDLE looks for changes
+     */
+    public record Settings(String host, int port, String hostname, boolean authWithoutTls, SslContext tls,
+                           boolean implicitTls, int maxLiteral, Duration idleTimeout, Duration idlePoll) {
+    }
+
+    /** A whole command and whether it arrived over TLS. */
+    record Command(byte[] bytes, boolean tls) {
+    }
+
+    private final Settings settings;
+    private final ImapStore store;
+    private final LoginGuard guard;
+    private DisposableServer server;
+
+    public ImapServer(Settings settings, ImapStore store) {
+        this(settings, store, LoginGuard.disabled());
+    }
+
+    public ImapServer(Settings settings, ImapStore store, LoginGuard guard) {
+        this.settings = settings;
+        this.store = store;
+        this.guard = guard;
+    }
+
+    public void start() {
+        if (settings.implicitTls() && settings.tls() == null) {
+            throw new IllegalStateException("Implicit TLS needs a certificate");
+        }
+        TcpServer tcp = TcpServer.create()
+                .host(settings.host())
+                .port(settings.port())
+                .doOnConnection(connection -> connection
+                        .addHandlerFirst("imap-idle", new ReadTimeoutHandler(settings.idleTimeout().toSeconds(), TimeUnit.SECONDS))
+                        .addHandlerLast("imap-commands", new CommandDecoder(settings.maxLiteral())));
+        if (settings.implicitTls()) {
+            tcp = tcp.secure(spec -> spec.sslContext(settings.tls()));
+        }
+        server = tcp.handle((inbound, outbound) -> {
+                    Connection[] connection = {null};
+                    String[] remoteIp = {"unknown"};
+                    inbound.withConnection(c -> {
+                        connection[0] = c;
+                        if (c.address() instanceof InetSocketAddress address && address.getAddress() != null) {
+                            remoteIp[0] = address.getAddress().getHostAddress();
+                        }
+                    });
+                    ImapSession session = new ImapSession(
+                            new ImapSession.Settings(settings.hostname(), settings.tls() != null, settings.authWithoutTls()),
+                            store, guard, remoteIp[0], settings.implicitTls());
+                    @SuppressWarnings("unchecked")
+                    Sinks.Empty<Void>[] idleDone = new Sinks.Empty[1];
+
+                    Flux<byte[]> responses = inbound.receiveObject().cast(Command.class)
+                            // DONE ends IDLE while the IDLE command is still running — handled before the queue
+                            .filter(command -> {
+                                if (session.idling() && isDone(command.bytes())) {
+                                    if (idleDone[0] != null) {
+                                        idleDone[0].tryEmitEmpty();
+                                    }
+                                    return false;
+                                }
+                                return true;
+                            })
+                            // read commands as they come (so DONE is seen during IDLE), run them one by one
+                            .onBackpressureBuffer(MAX_QUEUED, dropped -> log.warn("IMAP {}: too many queued commands", session.remoteIp))
+                            .concatMap(command -> {
+                                if (session.tls && !command.tls()) {
+                                    // plain text sent together with STARTTLS: never executed, the connection is closed
+                                    log.warn("IMAP {}: plain-text command after STARTTLS, closing", session.remoteIp);
+                                    session.closing = true;
+                                    connection[0].dispose();
+                                    return Flux.empty();
+                                }
+                                String text = new String(command.bytes(), StandardCharsets.UTF_8).trim();
+                                Matcher idle = IDLE.matcher(text);
+                                if (idle.matches()) {
+                                    idleDone[0] = Sinks.empty();
+                                    return idle(session, idle.group(1), idleDone[0]);
+                                }
+                                return blocking(() -> session.handle(command.bytes()));
+                            })
+                            .onErrorResume(e -> {
+                                log.debug("IMAP {}: connection closed: {}", session.remoteIp, e.toString());
+                                return Mono.just(ImapSession.line("* BYE " + e.getMessage()));
+                            })
+                            // after the tagged line of the command that closes (LOGOUT, too many failed logins), not after
+                            // its first untagged "* BYE" — the tagged answer must still reach the client
+                            .takeUntil(response -> session.closing && !untagged(response));
+
+                    return Flux.concat(Mono.just(session.greeting()), responses)
+                            .concatMap(response -> response == ImapSession.STARTTLS_READY
+                                    ? startTls(connection[0], session)
+                                    : send(outbound, response))
+                            .then();
+                })
+                .bindNow(Duration.ofSeconds(10));
+        log.info("IMAP server listening on {}:{} ({}{})", settings.host(), port(), settings.hostname(),
+                settings.implicitTls() ? ", implicit TLS" : settings.tls() != null ? ", STARTTLS" : ", no TLS");
+    }
+
+    private Flux<byte[]> idle(ImapSession session, String tag, Sinks.Empty<Void> done) {
+        Flux<byte[]> polls = Flux.interval(settings.idlePoll())
+                .onBackpressureDrop()
+                .concatMap(tick -> blocking(session::idlePoll))
+                .takeUntilOther(done.asMono())
+                .take(IDLE_MAX);
+        return Flux.concat(
+                blocking(() -> session.idleStart(tag)),
+                Flux.defer(() -> session.idling() ? polls : Flux.empty()),
+                blocking(session::idleEnd));
+    }
+
+    private static boolean isDone(byte[] bytes) {
+        return new String(bytes, StandardCharsets.US_ASCII).trim().toUpperCase(Locale.ROOT).equals("DONE");
+    }
+
+    private static boolean untagged(byte[] response) {
+        return response.length > 1 && response[0] == '*' && response[1] == ' ';
+    }
+
+    private static Flux<byte[]> blocking(java.util.concurrent.Callable<List<byte[]>> work) {
+        return Mono.fromCallable(work).subscribeOn(Schedulers.boundedElastic()).flatMapIterable(list -> list);
+    }
+
+    private static Mono<Void> send(NettyOutbound outbound, byte[] response) {
+        return outbound.send(Mono.just(Unpooled.wrappedBuffer(response))).then();
+    }
+
+    /** After the tagged OK of STARTTLS has left in plain text: TLS in front, a fresh decoder (no plain leftovers). */
+    private Mono<Void> startTls(Connection connection, ImapSession session) {
+        ChannelPipeline pipeline = connection.channel().pipeline();
+        SslHandler ssl = settings.tls().newHandler(connection.channel().alloc());
+        pipeline.replace("imap-commands", "imap-commands", new CommandDecoder(settings.maxLiteral()));
+        pipeline.addFirst("imap-tls", ssl);
+        return Mono.create(sink -> ssl.handshakeFuture().addListener(future -> {
+            if (!future.isSuccess()) {
+                log.info("IMAP {}: TLS handshake failed: {}", session.remoteIp, future.cause().toString());
+                session.closing = true;
+                connection.dispose();
+            }
+            sink.success();
+        }));
+    }
+
+    public int port() {
+        return server.port();
+    }
+
+    public void stop() {
+        if (server != null) {
+            server.disposeNow(Duration.ofSeconds(5));
+        }
+    }
+
+    /**
+     * Collects one command: lines plus the literals they announce. A synchronizing literal {n} gets "+ Ready" first;
+     * {n+} (LITERAL+) is read at once. Marks whether the command was read behind TLS.
+     */
+    static final class CommandDecoder extends ByteToMessageDecoder {
+        private final int maxLiteral;
+        private final ByteArrayOutputStream command = new ByteArrayOutputStream();
+        private int literalLeft;
+        private int lineBytes;
+
+        CommandDecoder(int maxLiteral) {
+            this.maxLiteral = maxLiteral;
+        }
+
+        @Override
+        protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) {
+            while (in.isReadable()) {
+                if (literalLeft > 0) {
+                    int n = Math.min(literalLeft, in.readableBytes());
+                    byte[] chunk = new byte[n];
+                    in.readBytes(chunk);
+                    command.write(chunk, 0, n);
+                    literalLeft -= n;
+                    continue;
+                }
+                int newline = in.indexOf(in.readerIndex(), in.writerIndex(), (byte) '\n');
+                if (newline < 0) {
+                    if (lineBytes + in.readableBytes() > MAX_LINE) {
+                        throw new TooLongFrameException("Command line too long");
+                    }
+                    return;
+                }
+                int length = newline - in.readerIndex() + 1;
+                if (lineBytes + length > MAX_LINE) {
+                    throw new TooLongFrameException("Command line too long");
+                }
+                byte[] line = new byte[length];
+                in.readBytes(line);
+                command.write(line, 0, line.length);
+                lineBytes += length;
+                Matcher literal = LITERAL.matcher(new String(line, StandardCharsets.ISO_8859_1));
+                if (literal.find()) {
+                    long size = Long.parseLong(literal.group(1));
+                    if (size > maxLiteral) {
+                        ctx.writeAndFlush(Unpooled.copiedBuffer("* BYE Literal too large\r\n", StandardCharsets.US_ASCII));
+                        throw new TooLongFrameException("Literal too large: " + size);
+                    }
+                    literalLeft = (int) size;
+                    if (literal.group(2).isEmpty()) {
+                        ctx.writeAndFlush(Unpooled.copiedBuffer("+ Ready for literal data\r\n", StandardCharsets.US_ASCII));
+                    }
+                    continue;
+                }
+                out.add(new Command(command.toByteArray(), ctx.pipeline().get(SslHandler.class) != null));
+                command.reset();
+                lineBytes = 0;
+            }
+        }
+    }
+}

backend/src/main/java/com/mailserver/imap/ImapStore.java

@@ -0,0 +1,91 @@
+package com.mailserver.imap;
+
+import java.time.Instant;
+import java.util.List;
+import java.util.Locale;
+
+/**
+ * Mailboxes and messages as IMAP sees them. Blocking: the IMAP server calls it from a worker thread,
+ * never from the network event loop.
+ */
+public interface ImapStore {
+
+    /** A refusal the client sees as "NO reason". */
+    final class Refused extends RuntimeException {
+        public Refused(String reason) {
+            super(reason);
+        }
+    }
+
+    record Account(long userId, String email) {
+    }
+
+    record Mailbox(long id, String name, boolean system, long uidValidity, long uidNext) {
+
+        boolean isInbox() {
+            return system && "INBOX".equalsIgnoreCase(name);
+        }
+
+        boolean isDrafts() {
+            return system && "Drafts".equals(name);
+        }
+
+        /** RFC 6154 attribute, or null. */
+        String specialUse() {
+            if (!system) {
+                return null;
+            }
+            return switch (name) {
+                case "Drafts" -> "\\Drafts";
+                case "Sent" -> "\\Sent";
+                case "Spam" -> "\\Junk";
+                case "Trash" -> "\\Trash";
+                default -> null;
+            };
+        }
+
+        boolean named(String other) {
+            return isInbox() ? "INBOX".equalsIgnoreCase(other) : name.toLowerCase(Locale.ROOT).equals(other.toLowerCase(Locale.ROOT));
+        }
+    }
+
+    record Entry(long id, long uid, boolean seen, boolean flagged, boolean answered, boolean deleted, Instant internalDate) {
+
+        Entry withFlags(boolean seen, boolean flagged, boolean answered, boolean deleted) {
+            return new Entry(id, uid, seen, flagged, answered, deleted, internalDate);
+        }
+    }
+
+    /** null — wrong user or password. */
+    Account authenticate(String username, String password);
+
+    List<Mailbox> mailboxes(long userId);
+
+    Mailbox create(long userId, String name);
+
+    void rename(long userId, Mailbox mailbox, String newName);
+
+    /** An own folder: its messages go to the Trash (as in the web client), then the folder is removed. */
+    void delete(long userId, Mailbox mailbox);
+
+    /** Messages of the folder in UID order. */
+    List<Entry> entries(long folderId);
+
+    /** The full MIME text of the message (the original one, or built once and kept). */
+    byte[] source(long messageId);
+
+    void setFlags(long messageId, boolean seen, boolean flagged, boolean answered, boolean deleted);
+
+    /** Stores the message into the folder; returns its UID. */
+    long append(long userId, Mailbox target, byte[] raw, boolean seen, boolean flagged, boolean answered,
+                boolean deleted, Instant internalDate);
+
+    /** Copies; returns the new UIDs in the same order. */
+    List<Long> copy(long userId, List<Entry> messages, Mailbox target);
+
+    /** Moves; returns the new UIDs in the same order. */
+    List<Long> move(long userId, List<Entry> messages, Mailbox target);
+
+    /** Removes the messages for good (with attachment files). */
+    void expunge(List<Long> messageIds);
+}

backend/src/main/java/com/mailserver/imap/ImapWriter.java

@@ -0,0 +1,255 @@
+package com.mailserver.imap;
+
+import jakarta.mail.internet.AddressException;
+import jakarta.mail.internet.ContentDisposition;
+import jakarta.mail.internet.InternetAddress;
+import jakarta.mail.internet.MimeUtility;
+import jakarta.mail.internet.ParameterList;
+import jakarta.mail.internet.ParseException;
+
+import java.io.ByteArrayOutputStream;
+import java.io.UnsupportedEncodingException;
+import java.nio.charset.StandardCharsets;
+import java.util.Enumeration;
+import java.util.Locale;
+
+/** Builds IMAP response bytes: strings, literals, ENVELOPE, BODYSTRUCTURE (RFC 3501 7.4.2). */
+final class ImapWriter {
+
+    private final ByteArrayOutputStream out = new ByteArrayOutputStream();
+
+    ImapWriter text(String text) {
+        byte[] bytes = text.getBytes(StandardCharsets.UTF_8);
+        out.write(bytes, 0, bytes.length);
+        return this;
+    }
+
+    ImapWriter sp() {
+        out.write(' ');
+        return this;
+    }
+
+    ImapWriter crlf() {
+        return text("\r\n");
+    }
+
+    ImapWriter literal(byte[] bytes) {
+        text("{" + bytes.length + "}\r\n");
+        out.write(bytes, 0, bytes.length);
+        return this;
+    }
+
+    /** Quoted when it is plain ASCII without CR/LF, a literal otherwise; null → NIL. */
+    ImapWriter nstring(String value) {
+        if (value == null) {
+            return text("NIL");
+        }
+        return string(value);
+    }
+
+    ImapWriter string(String value) {
+        boolean quotable = value.length() < 1024;
+        for (int i = 0; i < value.length() && quotable; i++) {
+            char c = value.charAt(i);
+            if (c > 0x7e || c < 0x20) {
+                quotable = false;
+            }
+        }
+        if (!quotable) {
+            return literal(value.getBytes(StandardCharsets.UTF_8));
+        }
+        return text("\"" + value.replace("\\", "\\\\").replace("\"", "\\\"") + "\"");
+    }
+
+    byte[] bytes() {
+        return out.toByteArray();
+    }
+
+    // ---------- ENVELOPE ----------
+
+    ImapWriter envelope(MimeTree message) {
+        text("(");
+        nstring(message.header("Date")).sp();
+        nstring(message.header("Subject")).sp();
+        String from = message.header("From");
+        addresses(from).sp();
+        addresses(firstNonNull(message.header("Sender"), from)).sp();
+        addresses(firstNonNull(message.header("Reply-To"), from)).sp();
+        addresses(message.header("To")).sp();
+        addresses(message.header("Cc")).sp();
+        addresses(message.header("Bcc")).sp();
+        nstring(message.header("In-Reply-To")).sp();
+        nstring(message.header("Message-ID"));
+        return text(")");
+    }
+
+    private ImapWriter addresses(String header) {
+        if (header == null || header.isBlank()) {
+            return text("NIL");
+        }
+        InternetAddress[] list;
+        try {
+            list = InternetAddress.parseHeader(header, false);
+        } catch (AddressException e) {
+            return text("NIL");
+        }
+        if (list.length == 0) {
+            return text("NIL");
+        }
+        text("(");
+        for (InternetAddress address : list) {
+            String email = address.getAddress() == null ? "" : address.getAddress();
+            int at = email.lastIndexOf('@');
+            text("(");
+            nstring(encodedPersonal(address.getPersonal())).sp().text("NIL").sp();
+            nstring(at > 0 ? email.substring(0, at) : email).sp();
+            nstring(at > 0 ? email.substring(at + 1) : null);
+            text(")");
+        }
+        return text(")");
+    }
+
+    private static String encodedPersonal(String personal) {
+        if (personal == null) {
+            return null;
+        }
+        try {
+            return MimeUtility.encodeWord(personal, "UTF-8", "B");
+        } catch (UnsupportedEncodingException e) {
+            return personal;
+        }
+    }
+
+    // ---------- BODYSTRUCTURE / BODY ----------
+
+    ImapWriter bodyStructure(MimeTree part, boolean extensible) {
+        text("(");
+        if (part.isMultipart() && !part.children.isEmpty()) {
+            for (MimeTree child : part.children) {
+                bodyStructure(child, extensible);
+            }
+            sp().string(part.type.getSubType().toUpperCase(Locale.ROOT));
+            if (extensible) {
+                sp().params(part.type.getParameterList()).sp();
+                disposition(part).sp().text("NIL NIL");
+            }
+            return text(")");
+        }
+        String primary = part.isMultipart() ? "TEXT" : part.type.getPrimaryType().toUpperCase(Locale.ROOT);
+        String sub = part.isMultipart() ? "PLAIN" : part.type.getSubType().toUpperCase(Locale.ROOT);
+        string(primary).sp().string(sub).sp();
+        params(part.type.getParameterList()).sp();
+        nstring(part.header("Content-ID")).sp();
+        nstring(part.header("Content-Description")).sp();
+        String encoding = part.header("Content-Transfer-Encoding");
+        string(encoding == null ? "7BIT" : encoding.toUpperCase(Locale.ROOT)).sp();
+        text(String.valueOf(part.bodySize()));
+        if ("TEXT".equals(primary)) {
+            sp().text(String.valueOf(part.bodyLines()));
+        } else if (part.message != null) {
+            sp().envelope(part.message).sp().bodyStructure(part.message, extensible).sp().text(String.valueOf(part.bodyLines()));
+        }
+        if (extensible) {
+            sp().nstring(part.header("Content-MD5")).sp();
+            disposition(part).sp();
+            nstring(part.header("Content-Language")).sp();
+            nstring(part.header("Content-Location"));
+        }
+        return text(")");
+    }
+
+    private ImapWriter params(ParameterList params) {
+        if (params == null || params.size() == 0) {
+            return text("NIL");
+        }
+        text("(");
+        boolean first = true;
+        Enumeration<String> names = params.getNames();
+        while (names.hasMoreElements()) {
+            String name = names.nextElement();
+            if (!first) {
+                sp();
+            }
+            first = false;
+            string(name.toUpperCase(Locale.ROOT)).sp().string(String.valueOf(params.get(name)));
+        }
+        return text(")");
+    }
+
+    private ImapWriter disposition(MimeTree part) {
+        String header = part.header("Content-Disposition");
+        if (header == null) {
+            return text("NIL");
+        }
+        try {
+            ContentDisposition disposition = new ContentDisposition(header);
+            text("(").string(disposition.getDisposition().toUpperCase(Locale.ROOT)).sp();
+            params(disposition.getParameterList());
+            return text(")");
+        } catch (ParseException e) {
+            return text("NIL");
+        }
+    }
+
+    private static String firstNonNull(String a, String b) {
+        return a != null ? a : b;
+    }
+
+    // ---------- modified UTF-7 (RFC 3501 5.1.3) for mailbox names ----------
+
+    static String encodeMailbox(String name) {
+        StringBuilder out = new StringBuilder();
+        StringBuilder pending = new StringBuilder();
+        for (int i = 0; i < name.length(); i++) {
+            char c = name.charAt(i);
+            if (c >= 0x20 && c <= 0x7e) {
+                flushBase64(out, pending);
+                out.append(c == '&' ? "&-" : String.valueOf(c));
+            } else {
+                pending.append(c);
+            }
+        }
+        flushBase64(out, pending);
+        return out.toString();
+    }
+
+    private static void flushBase64(StringBuilder out, StringBuilder pending) {
+        if (pending.length() == 0) {
+            return;
+        }
+        byte[] utf16 = pending.toString().getBytes(StandardCharsets.UTF_16BE);
+        String base64 = java.util.Base64.getEncoder().withoutPadding().encodeToString(utf16).replace('/', ',');
+        out.append('&').append(base64).append('-');
+        pending.setLength(0);
+    }
+
+    static String decodeMailbox(String name) {
+        StringBuilder out = new StringBuilder();
+        int i = 0;
+        while (i < name.length()) {
+            char c = name.charAt(i);
+            if (c != '&') {
+                out.append(c);
+                i++;
+                continue;
+            }
+            int dash = name.indexOf('-', i);
+            if (dash < 0) {
+                out.append(name.substring(i));
+                break;
+            }
+            if (dash == i + 1) {
+                out.append('&');
+            } else {
+                try {
+                    byte[] utf16 = java.util.Base64.getDecoder().decode(name.substring(i + 1, dash).replace(',', '/'));
+                    out.append(new String(utf16, StandardCharsets.UTF_16BE));
+                } catch (IllegalArgumentException e) {
+                    out.append(name, i, dash + 1);
+                }
+            }
+            i = dash + 1;
+        }
+        return out.toString();
+    }
+}

backend/src/main/java/com/mailserver/imap/MimeSource.java

@@ -0,0 +1,129 @@
+package com.mailserver.imap;
+
+import com.mailserver.domain.Attachment;
+import com.mailserver.domain.Message;
+import jakarta.activation.DataHandler;
+import jakarta.activation.FileDataSource;
+import jakarta.mail.MessagingException;
+import jakarta.mail.Session;
+import jakarta.mail.internet.InternetAddress;
+import jakarta.mail.internet.MimeBodyPart;
+import jakarta.mail.internet.MimeMessage;
+import jakarta.mail.internet.MimeMultipart;
+import jakarta.mail.internet.MimeUtility;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Date;
+import java.util.List;
+import java.util.Properties;
+
+/**
+ * MIME text of a message that has no original (written in the web client): built from the stored fields and
+ * attachment files. The boundary and Message-ID come from the message id, so the result is the same every time.
+ */
+public final class MimeSource {
+
+    private MimeSource() {
+    }
+
+    public static byte[] build(Message message, List<Attachment> attachments, String hostname)
+            throws MessagingException, IOException {
+        Properties props = new Properties();
+        props.put("mail.mime.splitlongparameters", "true");
+        Session session = Session.getInstance(props);
+        String messageId = message.getMessageId() == null || message.getMessageId().isBlank()
+                ? message.getId() + "@" + hostname
+                : message.getMessageId().replaceAll("^<|>$", "");
+        if (!messageId.contains("@")) {
+            messageId = messageId + "@" + hostname;
+        }
+        String finalMessageId = "<" + messageId + ">";
+        MimeMessage mime = new MimeMessage(session) {
+            @Override
+            protected void updateMessageID() throws MessagingException {
+                setHeader("Message-ID", finalMessageId);
+            }
+        };
+
+        String from = message.getSenderEmail() == null ? "unknown@" + hostname : message.getSenderEmail();
+        mime.setFrom(new InternetAddress(from, message.getSenderName(), "UTF-8"));
+        List<InternetAddress> to = addresses(message.getRecipientEmail());
+        if (!to.isEmpty()) {
+            mime.setRecipients(jakarta.mail.Message.RecipientType.TO, to.toArray(new InternetAddress[0]));
+        }
+        List<InternetAddress> cc = addresses(message.getCcEmail());
+        if (!cc.isEmpty()) {
+            mime.setRecipients(jakarta.mail.Message.RecipientType.CC, cc.toArray(new InternetAddress[0]));
+        }
+        mime.setSubject(message.getSubject() == null ? "" : message.getSubject(), "UTF-8");
+        if (message.getReceivedAt() != null) {
+            mime.setSentDate(Date.from(message.getReceivedAt()));
+        }
+
+        String body = message.getBody() == null ? "" : message.getBody();
+        String subtype = message.isHtml() ? "html" : "plain";
+        if (attachments.isEmpty()) {
+            mime.setText(body, "UTF-8", subtype);
+        } else {
+            MimeMultipart mixed = new FixedBoundaryMultipart("mixed", "=_rms_" + message.getId());
+            MimeBodyPart text = new MimeBodyPart();
+            text.setText(body, "UTF-8", subtype);
+            mixed.addBodyPart(text);
+            for (Attachment attachment : attachments) {
+                Path file = Path.of(attachment.getFilePath());
+                if (!Files.isRegularFile(file)) {
+                    continue;
+                }
+                MimeBodyPart part = new MimeBodyPart();
+                FileDataSource source = new FileDataSource(file.toFile()) {
+                    @Override
+                    public String getContentType() {
+                        return attachment.getContentType() == null ? "application/octet-stream" : attachment.getContentType();
+                    }
+                };
+                part.setDataHandler(new DataHandler(source));
+                part.setFileName(MimeUtility.encodeText(attachment.getFilename(), "UTF-8", null));
+                part.setDisposition(attachment.getContentId() != null ? MimeBodyPart.INLINE : MimeBodyPart.ATTACHMENT);
+                if (attachment.getContentId() != null) {
+                    part.setContentID("<" + attachment.getContentId().replaceAll("^<|>$", "") + ">");
+                }
+                mixed.addBodyPart(part);
+            }
+            mime.setContent(mixed);
+        }
+        mime.saveChanges();
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+        mime.writeTo(out);
+        return out.toByteArray();
+    }
+
+    private static List<InternetAddress> addresses(String list) {
+        List<InternetAddress> result = new ArrayList<>();
+        if (list == null || list.isBlank()) {
+            return result;
+        }
+        for (String one : list.split("[,;]")) {
+            String address = one.trim();
+            if (!address.isEmpty()) {
+                try {
+                    result.add(new InternetAddress(address));
+                } catch (MessagingException ignored) {
+                    // a broken address is left out, the message is still served
+                }
+            }
+        }
+        return result;
+    }
+
+    /** MimeMultipart with a given boundary instead of a random one. */
+    private static final class FixedBoundaryMultipart extends MimeMultipart {
+        FixedBoundaryMultipart(String subtype, String boundary) {
+            super(subtype);
+            this.contentType = "multipart/" + subtype + "; boundary=\"" + boundary + "\"";
+        }
+    }
+}

backend/src/main/java/com/mailserver/imap/MimeTree.java

@@ -0,0 +1,250 @@
+package com.mailserver.imap;
+
+import jakarta.mail.MessagingException;
+import jakarta.mail.internet.ContentType;
+import jakarta.mail.internet.InternetHeaders;
+import jakarta.mail.internet.ParseException;
+
+import java.io.ByteArrayInputStream;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Enumeration;
+import java.util.List;
+import java.util.Locale;
+import java.util.Set;
+
+/**
+ * A message split into MIME parts by byte offsets — what IMAP needs for BODYSTRUCTURE and BODY[section]:
+ * every part is a range of the original bytes, so sizes and contents match BODY[] exactly.
+ */
+final class MimeTree {
+
+    private static final int MAX_DEPTH = 20;
+
+    final byte[] raw;
+    /** Part = [start, end); headers = [start, bodyStart), the blank line included. */
+    final int start;
+    final int bodyStart;
+    final int end;
+    final InternetHeaders headers;
+    final ContentType type;
+    final List<MimeTree> children;
+    /** The encapsulated message of a message/rfc822 part. */
+    final MimeTree message;
+
+    private MimeTree(byte[] raw, int start, int end, int depth) {
+        this.raw = raw;
+        this.start = start;
+        this.end = end;
+        this.bodyStart = headerEnd(raw, start, end);
+        this.headers = parseHeaders(raw, start, bodyStart);
+        this.type = contentType(headers);
+        List<MimeTree> parts = new ArrayList<>();
+        MimeTree nested = null;
+        if (depth < MAX_DEPTH) {
+            if (isMultipart()) {
+                String boundary = type.getParameter("boundary");
+                if (boundary != null && !boundary.isEmpty()) {
+                    split(boundary, depth, parts);
+                }
+            } else if (is("message", "rfc822") || is("message", "global")) {
+                nested = new MimeTree(raw, bodyStart, end, depth + 1);
+            }
+        }
+        this.children = Collections.unmodifiableList(parts);
+        this.message = nested;
+    }
+
+    static MimeTree parse(byte[] raw) {
+        return new MimeTree(raw, 0, raw.length, 0);
+    }
+
+    boolean isMultipart() {
+        return "multipart".equalsIgnoreCase(type.getPrimaryType());
+    }
+
+    boolean is(String primary, String sub) {
+        return primary.equalsIgnoreCase(type.getPrimaryType()) && sub.equalsIgnoreCase(type.getSubType());
+    }
+
+    byte[] all() {
+        return slice(start, end);
+    }
+
+    byte[] header() {
+        return slice(start, bodyStart);
+    }
+
+    byte[] body() {
+        return slice(bodyStart, end);
+    }
+
+    int bodySize() {
+        return end - bodyStart;
+    }
+
+    /** Lines of the body (for text parts in BODYSTRUCTURE). */
+    int bodyLines() {
+        int lines = 0;
+        for (int i = bodyStart; i < end; i++) {
+            if (raw[i] == '\n') {
+                lines++;
+            }
+        }
+        if (end > bodyStart && raw[end - 1] != '\n') {
+            lines++;
+        }
+        return lines;
+    }
+
+    /** Header value unfolded, or null. */
+    String header(String name) {
+        String[] values = headers.getHeader(name);
+        if (values == null || values.length == 0 || values[0] == null) {
+            return null;
+        }
+        return values[0].replaceAll("\r?\n(?=[ \t])", "").trim();
+    }
+
+    /** Only these header fields (or all but these), each with its folded lines, plus the blank line. */
+    byte[] headerFields(Set<String> names, boolean not) {
+        StringBuilder out = new StringBuilder();
+        String text = new String(raw, start, bodyStart - start, StandardCharsets.ISO_8859_1);
+        String[] lines = text.split("\r?\n", -1);
+        boolean keep = false;
+        for (String line : lines) {
+            if (line.isEmpty()) {
+                continue;
+            }
+            if (line.charAt(0) == ' ' || line.charAt(0) == '\t') {
+                if (keep) {
+                    out.append(line).append("\r\n");
+                }
+                continue;
+            }
+            int colon = line.indexOf(':');
+            String name = colon > 0 ? line.substring(0, colon).trim().toUpperCase(Locale.ROOT) : "";
+            keep = names.contains(name) != not;
+            if (keep) {
+                out.append(line).append("\r\n");
+            }
+        }
+        out.append("\r\n");
+        return out.toString().getBytes(StandardCharsets.ISO_8859_1);
+    }
+
+    private byte[] slice(int from, int to) {
+        byte[] copy = new byte[Math.max(0, to - from)];
+        System.arraycopy(raw, from, copy, 0, copy.length);
+        return copy;
+    }
+
+    /** Body parts between "--boundary" lines; the CRLF before a delimiter belongs to the delimiter. */
+    private void split(String boundary, int depth, List<MimeTree> parts) {
+        byte[] delimiter = ("--" + boundary).getBytes(StandardCharsets.ISO_8859_1);
+        int partStart = -1;
+        int i = bodyStart;
+        while (i < end) {
+            int lineEnd = indexOf(raw, (byte) '\n', i, end);
+            int next = lineEnd < 0 ? end : lineEnd + 1;
+            if (startsWith(raw, i, end, delimiter)) {
+                int after = i + delimiter.length;
+                boolean close = after + 1 < end && raw[after] == '-' && raw[after + 1] == '-';
+                if (partStart >= 0) {
+                    int partEnd = i;
+                    if (partEnd > partStart && raw[partEnd - 1] == '\n') {
+                        partEnd--;
+                        if (partEnd > partStart && raw[partEnd - 1] == '\r') {
+                            partEnd--;
+                        }
+                    }
+                    parts.add(new MimeTree(raw, partStart, Math.max(partStart, partEnd), depth + 1));
+                }
+                if (close) {
+                    return;
+                }
+                partStart = next;
+            }
+            i = next;
+        }
+        if (partStart >= 0 && partStart < end) { // no closing delimiter — take the rest
+            parts.add(new MimeTree(raw, partStart, end, depth + 1));
+        }
+    }
+
+    private static int headerEnd(byte[] raw, int start, int end) {
+        if (start < end && raw[start] == '\n') {
+            return start + 1;
+        }
+        if (start + 1 < end && raw[start] == '\r' && raw[start + 1] == '\n') {
+            return start + 2;
+        }
+        for (int i = start; i < end; i++) {
+            if (raw[i] == '\n') {
+                if (i + 1 < end && raw[i + 1] == '\n') {
+                    return i + 2;
+                }
+                if (i + 2 < end && raw[i + 1] == '\r' && raw[i + 2] == '\n') {
+                    return i + 3;
+                }
+            }
+        }
+        return end; // headers only
+    }
+
+    private static InternetHeaders parseHeaders(byte[] raw, int start, int end) {
+        try {
+            return new InternetHeaders(new ByteArrayInputStream(raw, start, end - start));
+        } catch (MessagingException e) {
+            return new InternetHeaders();
+        }
+    }
+
+    private static ContentType contentType(InternetHeaders headers) {
+        String[] values = headers.getHeader("Content-Type");
+        if (values != null && values.length > 0 && values[0] != null) {
+            try {
+                return new ContentType(values[0].replaceAll("\r?\n(?=[ \t])", "").trim());
+            } catch (ParseException ignored) {
+                // broken header — the RFC 2045 default
+            }
+        }
+        try {
+            return new ContentType("text/plain; charset=us-ascii");
+        } catch (ParseException e) {
+            throw new IllegalStateException(e);
+        }
+    }
+
+    private static boolean startsWith(byte[] raw, int at, int end, byte[] prefix) {
+        if (at + prefix.length > end) {
+            return false;
+        }
+        for (int i = 0; i < prefix.length; i++) {
+            if (raw[at + i] != prefix[i]) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private static int indexOf(byte[] raw, byte value, int from, int end) {
+        for (int i = from; i < end; i++) {
+            if (raw[i] == value) {
+                return i;
+            }
+        }
+        return -1;
+    }
+
+    /** Header names of the part, for tests and debugging. */
+    List<String> headerNames() {
+        List<String> names = new ArrayList<>();
+        Enumeration<jakarta.mail.Header> all = headers.getAllHeaders();
+        while (all.hasMoreElements()) {
+            names.add(all.nextElement().getName());
+        }
+        return names;
+    }
+}

backend/src/main/java/com/mailserver/repository/MessageRepository.java

@@ -15,10 +15,6 @@ public interface MessageRepository extends R2dbcRepository<Message, Long> {
 
     Flux<Message> findByFolderId(Long folderId);
 
-    /** IMAP (switched off): the whole folder, newest first. */
-    @Query("SELECT * FROM messages WHERE folder_id = :#{#folderId} ORDER BY received_at DESC")
-    Flux<Message> findByFolderId(Long folderId, Pageable pageable);
-
     @Query("SELECT COUNT(*) FROM messages WHERE folder_id = :#{#folderId}")
     Mono<Long> countByFolderId(Long folderId);
 

backend/src/main/java/com/mailserver/security/LoginGuard.java

@@ -0,0 +1,257 @@
+package com.mailserver.security;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.scheduling.annotation.Scheduled;
+
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.ArrayDeque;
+import java.util.Deque;
+import java.util.LinkedHashMap;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * Brute-force protection for every place that checks a password: SMTP AUTH, IMAP LOGIN/AUTHENTICATE, web login,
+ * password change. One instance is shared by all of them, so failures on SMTP and IMAP add up.
+ * <ul>
+ *   <li><b>By IP:</b> {@code maxPerIp} failures within {@code window} → the IP is blocked for {@code block};
+ *       each next block of the same IP is twice as long, up to {@code maxBlock}.</li>
+ *   <li><b>By mailbox:</b> {@code maxPerAccount} failures within {@code window} from any IPs (a distributed attack on
+ *       one mailbox) → the mailbox is blocked for {@code block} — but not for IPs that logged in to it successfully
+ *       before ({@code knownIpTtl}), so an attacker cannot lock the owner's own mail program out.</li>
+ * </ul>
+ * While blocked the password is not checked at all (no answer to a guess) and the caller gets {@link #retryAfter}.
+ * State is in memory: a restart forgets it, which is fine for minutes-long blocks.
+ */
+public class LoginGuard {
+
+    private static final Logger log = LoggerFactory.getLogger(LoginGuard.class);
+
+    /** Upper bound of tracked keys of each kind, so a flood of random usernames/IPs cannot eat the memory. */
+    static final int MAX_KEYS = 100_000;
+    private static final int MAX_KNOWN_IPS_PER_ACCOUNT = 20;
+
+    public record Settings(boolean enabled, int maxPerIp, int maxPerAccount, Duration window, Duration block,
+                           Duration maxBlock, Duration knownIpTtl, Set<String> trustedIps, Duration failureDelay) {
+
+        public static Settings defaults() {
+            return new Settings(true, 10, 20, Duration.ofMinutes(15), Duration.ofMinutes(15), Duration.ofHours(24),
+                    Duration.ofDays(30), Set.of(), Duration.ofSeconds(1));
+        }
+    }
+
+    /** Failures in the window, current block and how many times the key was blocked in a row. */
+    private static final class Counter {
+        final Deque<Instant> failures = new ArrayDeque<>();
+        volatile Instant blockedUntil = Instant.EPOCH;
+        int strikes;
+        Instant lastSeen = Instant.EPOCH;
+    }
+
+    private final Settings settings;
+    private final Clock clock;
+    private final Map<String, Counter> byIp = new ConcurrentHashMap<>();
+    private final Map<String, Counter> byAccount = new ConcurrentHashMap<>();
+    /** account → IPs that logged in to it successfully, with the time of the last success. */
+    private final Map<String, Map<String, Instant>> knownIps = new ConcurrentHashMap<>();
+
+    public LoginGuard(Settings settings) {
+        this(settings, Clock.systemUTC());
+    }
+
+    LoginGuard(Settings settings, Clock clock) {
+        this.settings = settings;
+        this.clock = clock;
+    }
+
+    /** Guard that never blocks (tests, closed networks). */
+    public static LoginGuard disabled() {
+        Settings d = Settings.defaults();
+        return new LoginGuard(new Settings(false, d.maxPerIp(), d.maxPerAccount(), d.window(), d.block(), d.maxBlock(),
+                d.knownIpTtl(), Set.of(), Duration.ZERO));
+    }
+
+    /** Pause before answering "wrong password": slows down guessing inside one connection. */
+    public Duration failureDelay() {
+        return settings.enabled() ? settings.failureDelay() : Duration.ZERO;
+    }
+
+    /**
+     * Zero when the attempt may go on and the password may be checked; otherwise how long the caller has to wait.
+     */
+    public Duration retryAfter(String ip, String account) {
+        if (!settings.enabled()) {
+            return Duration.ZERO;
+        }
+        Instant now = clock.instant();
+        Duration wait = Duration.ZERO;
+        if (!trusted(ip)) {
+            wait = remaining(byIp.get(ip), now);
+        }
+        String acc = normalize(account);
+        if (acc != null && !known(acc, ip, now)) {
+            Duration accountWait = remaining(byAccount.get(acc), now);
+            if (accountWait.compareTo(wait) > 0) {
+                wait = accountWait;
+            }
+        }
+        return wait;
+    }
+
+    public boolean blocked(String ip, String account) {
+        return !retryAfter(ip, account).isZero();
+    }
+
+    /** A wrong password (or an unknown mailbox). */
+    public void failure(String ip, String account) {
+        if (!settings.enabled()) {
+            return;
+        }
+        Instant now = clock.instant();
+        if (!trusted(ip)) {
+            count(byIp, ip, settings.maxPerIp(), now, "IP " + ip);
+        }
+        String acc = normalize(account);
+        if (acc != null) {
+            count(byAccount, acc, settings.maxPerAccount(), now, "mailbox " + acc);
+        }
+    }
+
+    /** A right password: the IP becomes known for the mailbox, failures of this IP are forgiven. */
+    public void success(String ip, String account) {
+        if (!settings.enabled()) {
+            return;
+        }
+        Instant now = clock.instant();
+        String acc = normalize(account);
+        if (acc != null) {
+            if (knownIps.size() < MAX_KEYS || knownIps.containsKey(acc)) {
+                knownIps.compute(acc, (k, ips) -> {
+                    Map<String, Instant> map = ips != null ? ips : new LinkedHashMap<>();
+                    synchronized (map) {
+                        map.remove(ip);
+                        map.put(ip, now);
+                        while (map.size() > MAX_KNOWN_IPS_PER_ACCOUNT) {
+                            map.remove(map.keySet().iterator().next());
+                        }
+                    }
+                    return map;
+                });
+            }
+        }
+        byIp.computeIfPresent(ip, (k, c) -> {
+            c.failures.clear();
+            return c.blockedUntil.isAfter(now) ? c : null;
+        });
+    }
+
+    /** Drops what expired; runs every minute. */
+    @Scheduled(fixedDelay = 60_000)
+    public void sweep() {
+        Instant now = clock.instant();
+        Instant idle = now.minus(settings.maxBlock()).minus(settings.window());
+        byIp.entrySet().removeIf(e -> stale(e.getValue(), now, idle));
+        byAccount.entrySet().removeIf(e -> stale(e.getValue(), now, idle));
+        Instant knownSince = now.minus(settings.knownIpTtl());
+        knownIps.entrySet().removeIf(e -> {
+            synchronized (e.getValue()) {
+                e.getValue().values().removeIf(t -> t.isBefore(knownSince));
+                return e.getValue().isEmpty();
+            }
+        });
+    }
+
+    int trackedIps() {
+        return byIp.size();
+    }
+
+    int trackedAccounts() {
+        return byAccount.size();
+    }
+
+    // ---------------------------------------------------------------------------------------------
+
+    private void count(Map<String, Counter> map, String key, int max, Instant now, String what) {
+        if (map.size() >= MAX_KEYS && !map.containsKey(key)) {
+            sweep();
+            if (map.size() >= MAX_KEYS) {
+                log.warn("login guard: {} keys tracked, {} not counted", map.size(), what);
+                return;
+            }
+        }
+        map.compute(key, (k, existing) -> {
+            Counter c = existing != null ? existing : new Counter();
+            c.lastSeen = now;
+            Instant from = now.minus(settings.window());
+            while (!c.failures.isEmpty() && c.failures.peekFirst().isBefore(from)) {
+                c.failures.pollFirst();
+            }
+            if (c.blockedUntil.isAfter(now)) {
+                return c; // already blocked: attempts are refused before the password check anyway
+            }
+            // A long quiet time after the last block forgives the strikes
+            if (c.strikes > 0 && c.blockedUntil.plus(settings.maxBlock()).isBefore(now)) {
+                c.strikes = 0;
+            }
+            c.failures.addLast(now);
+            if (c.failures.size() >= max) {
+                Duration block = settings.block().multipliedBy(1L << Math.min(c.strikes, 20));
+                if (block.compareTo(settings.maxBlock()) > 0) {
+                    block = settings.maxBlock();
+                }
+                c.strikes++;
+                c.blockedUntil = now.plus(block);
+                c.failures.clear();
+                log.warn("login guard: {} blocked for {} after {} failed logins (block #{})",
+                        what, human(block), max, c.strikes);
+            }
+            return c;
+        });
+    }
+
+    private static Duration remaining(Counter c, Instant now) {
+        if (c == null) {
+            return Duration.ZERO;
+        }
+        Instant until = c.blockedUntil;
+        return until.isAfter(now) ? Duration.between(now, until) : Duration.ZERO;
+    }
+
+    private boolean known(String account, String ip, Instant now) {
+        Map<String, Instant> ips = knownIps.get(account);
+        if (ips == null) {
+            return false;
+        }
+        synchronized (ips) {
+            Instant at = ips.get(ip);
+            return at != null && at.plus(settings.knownIpTtl()).isAfter(now);
+        }
+    }
+
+    private boolean trusted(String ip) {
+        return settings.trustedIps().contains(ip);
+    }
+
+    private static boolean stale(Counter c, Instant now, Instant idle) {
+        return !c.blockedUntil.isAfter(now) && c.lastSeen.isBefore(idle);
+    }
+
+    private static String normalize(String account) {
+        if (account == null) {
+            return null;
+        }
+        String acc = account.trim().toLowerCase(Locale.ROOT);
+        return acc.isEmpty() ? null : acc;
+    }
+
+    /** "15 min" / "2 h" for messages to the user. */
+    public static String human(Duration d) {
+        long minutes = Math.max(1, (d.toSeconds() + 59) / 60);
+        return minutes < 120 ? minutes + " min" : (minutes + 59) / 60 + " h";
+    }
+}

backend/src/main/java/com/mailserver/service/LocalDelivery.java

@@ -38,9 +38,12 @@ public class LocalDelivery implements DeliveryWorker.BounceSender {
     private final SpfService spfService;
     private final DmarcService dmarcService;
     private final String hostname;
+    private final MessageSources sources;
 
     public LocalDelivery(MailService mailService, DkimService dkimService, SpfService spfService,
-                         DmarcService dmarcService, @Value("${mailserver.smtp.hostname:localhost}") String hostname) {
+                         DmarcService dmarcService, @Value("${mailserver.smtp.hostname:localhost}") String hostname,
+                         MessageSources sources) {
+        this.sources = sources;
         this.mailService = mailService;
         this.dkimService = dkimService;
         this.spfService = spfService;
@@ -82,11 +85,13 @@ public class LocalDelivery implements DeliveryWorker.BounceSender {
             for (FilePart file : attachments(mime)) {
                 mailService.storeIncomingAttachment(stored.getId(), file.name(), file.contentType(), file.bytes());
             }
+            // IMAP serves the message exactly as it arrived
+            sources.put(stored.getId(), raw).block();
         }
     }
 
     /** "a@x, b@y" from a header, or null. A broken header is ignored, not a reason to lose the message. */
-    static String addresses(MimeMessage mime, jakarta.mail.Message.RecipientType type) {
+    public static String addresses(MimeMessage mime, jakarta.mail.Message.RecipientType type) {
         try {
             jakarta.mail.Address[] list = mime.getRecipients(type);
             if (list == null || list.length == 0) {
@@ -103,11 +108,11 @@ public class LocalDelivery implements DeliveryWorker.BounceSender {
         }
     }
 
-    record FilePart(String name, String contentType, byte[] bytes) {
+    public record FilePart(String name, String contentType, byte[] bytes) {
     }
 
     /** Parts with a file name (attachments and inline images), nested multiparts walked. */
-    static List<FilePart> attachments(Part part) throws MessagingException, IOException {
+    public static List<FilePart> attachments(Part part) throws MessagingException, IOException {
         List<FilePart> files = new ArrayList<>();
         collect(part, files);
         return files;
@@ -144,11 +149,11 @@ public class LocalDelivery implements DeliveryWorker.BounceSender {
         }
     }
 
-    record Body(String text, boolean html) {
+    public record Body(String text, boolean html) {
     }
 
     /** HTML part when the message has one, otherwise the plain text; nested multiparts are walked. */
-    static Body body(Part part) throws MessagingException, IOException {
+    public static Body body(Part part) throws MessagingException, IOException {
         String html = find(part, "text/html");
         if (html != null) {
             return new Body(html, true);

backend/src/main/java/com/mailserver/service/MailService.java

@@ -59,7 +59,8 @@ public class MailService {
     public MailService(MessageRepository messageRepository, FolderRepository folderRepository,
                        UserRepository userRepository, AttachmentRepository attachmentRepository,
                        ContactRepository contactRepository,
-                       SpamFilterService spamFilterService) {
+                       SpamFilterService spamFilterService, MessageSources sources) {
+        this.sources = sources;
         this.messageRepository = messageRepository;
         this.folderRepository = folderRepository;
         this.userRepository = userRepository;
@@ -69,6 +70,8 @@ public class MailService {
     }
 
     /** System folders in the order the web client shows them; the rest — own folders, by name. */
+    private final MessageSources sources;
+
     public static final List<String> SYSTEM_FOLDERS = List.of("INBOX", "Drafts", "Sent", "Spam", "Trash");
 
     /** Messages per folder in one list — the web client sorts and pages them itself. */
@@ -212,6 +215,8 @@ public class MailService {
                     message.setMessageSize((long) (subject.length() + body.length()));
                     return messageRepository.save(message);
                 })
+                // IMAP: the draft changed — its MIME text is built anew
+                .flatMap(saved -> sources.remove(saved.getId()).thenReturn(saved))
                 .flatMap(this::withAttachmentCount);
     }
 
@@ -226,6 +231,7 @@ public class MailService {
     /** After sending: the draft's attachments move to the copy in Sent, the draft itself is removed. */
     public Mono<Void> finishDraft(Long draftId, Long sentMessageId) {
         return attachmentRepository.moveAll(draftId, sentMessageId)
+                .then(sources.remove(sentMessageId))
                 .then(messageRepository.deleteById(draftId));
     }
 
@@ -467,7 +473,7 @@ public class MailService {
                     attachment.setContentType(contentType);
                     attachment.setSizeBytes(sizeBytes);
                     attachment.setFilePath(filePath);
-                    return attachmentRepository.save(attachment);
+                    return sources.remove(messageId).then(attachmentRepository.save(attachment));
                 })
                 .map(this::toAttachmentResponse);
     }
@@ -491,7 +497,7 @@ public class MailService {
         return ownedAttachment(attachmentId, userId)
                 .flatMap(attachment -> {
                     deleteFile(attachment.getFilePath());
-                    return attachmentRepository.delete(attachment);
+                    return sources.remove(attachment.getMessageId()).then(attachmentRepository.delete(attachment));
                 });
     }
 

backend/src/main/java/com/mailserver/service/MessageSources.java

@@ -0,0 +1,38 @@
+package com.mailserver.service;
+
+import org.springframework.r2dbc.core.DatabaseClient;
+import org.springframework.stereotype.Component;
+import reactor.core.publisher.Mono;
+
+/**
+ * The message exactly as received or appended (table message_sources). IMAP serves it as BODY[]; a message without
+ * one gets its MIME text built once ({@link com.mailserver.imap.MimeSource}). A changed draft loses it.
+ */
+@Component
+public class MessageSources {
+
+    private final DatabaseClient db;
+
+    public MessageSources(DatabaseClient db) {
+        this.db = db;
+    }
+
+    public Mono<byte[]> get(Long messageId) {
+        return db.sql("SELECT raw FROM message_sources WHERE message_id = :id")
+                .bind("id", messageId)
+                .map(row -> row.get("raw", byte[].class))
+                .one();
+    }
+
+    public Mono<Void> put(Long messageId, byte[] raw) {
+        return db.sql("INSERT INTO message_sources (message_id, raw) VALUES (:id, :raw) "
+                        + "ON CONFLICT (message_id) DO UPDATE SET raw = EXCLUDED.raw")
+                .bind("id", messageId)
+                .bind("raw", raw)
+                .then();
+    }
+
+    public Mono<Void> remove(Long messageId) {
+        return db.sql("DELETE FROM message_sources WHERE message_id = :id").bind("id", messageId).then();
+    }
+}

backend/src/main/java/com/mailserver/smtp/ReloadingKeyManager.java

@@ -0,0 +1,194 @@
+package com.mailserver.smtp;
+
+import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;
+import org.bouncycastle.openssl.PEMKeyPair;
+import org.bouncycastle.openssl.PEMParser;
+import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.net.ssl.SSLEngine;
+import javax.net.ssl.X509ExtendedKeyManager;
+import java.io.InputStream;
+import java.io.Reader;
+import java.net.Socket;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.attribute.FileTime;
+import java.security.Principal;
+import java.security.PrivateKey;
+import java.security.cert.CertificateFactory;
+import java.security.cert.X509Certificate;
+import java.time.Clock;
+import java.time.Duration;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * Server certificate and key from PEM files, read again when the files change — a Let's Encrypt certificate
+ * renewed on disk (lego, certbot) is picked up without a restart, for STARTTLS and implicit TLS alike: the JDK
+ * asks the key manager on every handshake. The files are checked at most once per {@code interval}; a file
+ * that cannot be read (a renewal half written) keeps the previous certificate and is tried again next time.
+ * <p>
+ * Key: PKCS#8 ({@code PRIVATE KEY}) or the traditional {@code RSA PRIVATE KEY} / {@code EC PRIVATE KEY} that
+ * lego and certbot write. Each loaded pair gets its own alias, so a handshake that asks for the chain and then
+ * for the key never mixes two generations.
+ */
+public final class ReloadingKeyManager extends X509ExtendedKeyManager {
+
+    private static final Logger log = LoggerFactory.getLogger(ReloadingKeyManager.class);
+    private static final String ALIAS_PREFIX = "mail-";
+
+    record Material(String alias, X509Certificate[] chain, PrivateKey key, FileTime certTime, FileTime keyTime) {
+    }
+
+    private final Path certFile;
+    private final Path keyFile;
+    private final Duration interval;
+    private final Clock clock;
+    /** The current pair and the one before it (a handshake may still hold its alias) */
+    private final Map<String, Material> byAlias = new ConcurrentHashMap<>();
+    private volatile Material current;
+    private volatile long checkedAt;
+    private int generation;
+
+    public ReloadingKeyManager(Path certFile, Path keyFile, Duration interval, Clock clock) throws Exception {
+        this.certFile = certFile;
+        this.keyFile = keyFile;
+        this.interval = interval;
+        this.clock = clock;
+        install(load());
+        this.checkedAt = clock.millis();
+    }
+
+    /** The pair to use now; reads the files again when the interval has passed and they changed */
+    Material material() {
+        long now = clock.millis();
+        if (now - checkedAt >= interval.toMillis()) {
+            synchronized (this) {
+                if (now - checkedAt >= interval.toMillis()) {
+                    checkedAt = now;
+                    reloadIfChanged();
+                }
+            }
+        }
+        return current;
+    }
+
+    private void reloadIfChanged() {
+        Material old = current;
+        try {
+            if (Files.getLastModifiedTime(certFile).equals(old.certTime())
+                    && Files.getLastModifiedTime(keyFile).equals(old.keyTime())) {
+                return;
+            }
+            Material fresh = load();
+            install(fresh);
+            log.info("TLS: certificate {} reloaded, valid until {}", certFile, fresh.chain()[0].getNotAfter());
+        } catch (Exception e) {
+            log.warn("TLS: cannot read {} / {} ({}), keeping the certificate valid until {}",
+                    certFile, keyFile, e.toString(), old.chain()[0].getNotAfter());
+        }
+    }
+
+    private synchronized void install(Material material) {
+        Material previous = current;
+        byAlias.keySet().removeIf(alias -> previous == null || !alias.equals(previous.alias()));
+        byAlias.put(material.alias(), material);
+        current = material;
+    }
+
+    private Material load() throws Exception {
+        FileTime certTime = Files.getLastModifiedTime(certFile);
+        FileTime keyTime = Files.getLastModifiedTime(keyFile);
+        X509Certificate[] chain;
+        try (InputStream in = Files.newInputStream(certFile)) {
+            chain = CertificateFactory.getInstance("X.509").generateCertificates(in).stream()
+                    .map(X509Certificate.class::cast).toArray(X509Certificate[]::new);
+        }
+        if (chain.length == 0) {
+            throw new IllegalStateException("no certificate in " + certFile);
+        }
+        PrivateKey key = readKey(keyFile);
+        if (!chain[0].getPublicKey().getAlgorithm().equals(key.getAlgorithm())) {
+            throw new IllegalStateException("the key in " + keyFile + " is " + key.getAlgorithm()
+                    + ", the certificate is " + chain[0].getPublicKey().getAlgorithm());
+        }
+        String alias;
+        synchronized (this) {
+            alias = ALIAS_PREFIX + (++generation);
+        }
+        return new Material(alias, chain, key, certTime, keyTime);
+    }
+
+    static PrivateKey readKey(Path file) throws Exception {
+        try (Reader reader = Files.newBufferedReader(file, StandardCharsets.US_ASCII);
+             PEMParser parser = new PEMParser(reader)) {
+            Object object;
+            while ((object = parser.readObject()) != null) {
+                JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
+                if (object instanceof PrivateKeyInfo info) {
+                    return converter.getPrivateKey(info);
+                }
+                if (object instanceof PEMKeyPair pair) {
+                    return converter.getPrivateKey(pair.getPrivateKeyInfo()); // SEC1 may come without the public part
+                }
+                // EC PARAMETERS before EC PRIVATE KEY (openssl ecparam -genkey) — skip
+            }
+        }
+        throw new IllegalStateException("no private key in " + file);
+    }
+
+    private String serverAlias(String keyType) {
+        Material material = material();
+        String algorithm = material.key().getAlgorithm();
+        boolean fits = keyType == null || keyType.equalsIgnoreCase(algorithm)
+                || ("RSA".equals(algorithm) && keyType.equalsIgnoreCase("RSASSA-PSS"))
+                || ("EC".equals(algorithm) && keyType.toUpperCase().startsWith("EC"));
+        return fits ? material.alias() : null;
+    }
+
+    @Override
+    public String chooseServerAlias(String keyType, Principal[] issuers, Socket socket) {
+        return serverAlias(keyType);
+    }
+
+    @Override
+    public String chooseEngineServerAlias(String keyType, Principal[] issuers, SSLEngine engine) {
+        return serverAlias(keyType);
+    }
+
+    @Override
+    public String[] getServerAliases(String keyType, Principal[] issuers) {
+        String alias = serverAlias(keyType);
+        return alias == null ? null : new String[]{alias};
+    }
+
+    @Override
+    public X509Certificate[] getCertificateChain(String alias) {
+        Material material = alias == null ? null : byAlias.get(alias);
+        return material == null ? null : material.chain().clone();
+    }
+
+    @Override
+    public PrivateKey getPrivateKey(String alias) {
+        Material material = alias == null ? null : byAlias.get(alias);
+        return material == null ? null : material.key();
+    }
+
+    @Override
+    public String[] getClientAliases(String keyType, Principal[] issuers) {
+        return null;
+    }
+
+    @Override
+    public String chooseClientAlias(String[] keyType, Principal[] issuers, Socket socket) {
+        return null;
+    }
+
+    @Override
+    public String chooseEngineClientAlias(String[] keyType, Principal[] issuers, SSLEngine engine) {
+        return null;
+    }
+}

backend/src/main/java/com/mailserver/smtp/SmtpServer.java

@@ -1,13 +1,23 @@
 package com.mailserver.smtp;
 
+import com.mailserver.security.LoginGuard;
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufUtil;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelPipeline;
 import io.netty.handler.codec.LineBasedFrameDecoder;
+import io.netty.handler.codec.MessageToMessageDecoder;
+import io.netty.handler.ssl.SslContext;
+import io.netty.handler.ssl.SslHandler;
 import io.netty.handler.timeout.ReadTimeoutHandler;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.core.scheduler.Schedulers;
+import reactor.netty.Connection;
 import reactor.netty.DisposableServer;
+import reactor.netty.NettyOutbound;
 import reactor.netty.tcp.TcpServer;
 
 import java.io.ByteArrayOutputStream;
@@ -32,7 +42,10 @@ import java.util.concurrent.TimeUnit;
  *   <li>the message is stored or queued before the client gets 250 — on failure 451 and the client retries;</li>
  *   <li>database and DNS work runs on a worker thread, not on the event loop.</li>
  * </ul>
- * No STARTTLS yet: AUTH is offered only when {@code authWithoutTls} is on (a closed network: inside a VM or a docker network).
+ * TLS (RFC 3207 STARTTLS, or implicit TLS on a separate port, RFC 8314): with a {@code tls} context STARTTLS is
+ * offered; AUTH only over TLS, or without it when {@code authWithoutTls} is on (a closed network: VM, docker network).
+ * After STARTTLS the session starts over (new EHLO), and lines sent in plain text together with STARTTLS are not
+ * executed — the connection is closed (command injection, CVE-2011-0411).
  */
 public class SmtpServer {
 
@@ -42,47 +55,116 @@ public class SmtpServer {
     static final int MAX_LINE = 64 * 1024;
     static final int MAX_RECIPIENTS = 100;
     private static final int MAX_BAD_COMMANDS = 20;
+    /** Wrong passwords in one connection before it is closed. */
+    private static final int MAX_AUTH_FAILURES = 3;
+    // Compared by identity: TLS starts right after exactly this reply is written
+    private static final String STARTTLS_READY = new String("220 2.0.0 Ready to start TLS\r\n");
 
+    /**
+     * @param tls         certificate for STARTTLS / implicit TLS; null — no TLS
+     * @param implicitTls TLS from the first byte (port 465), no STARTTLS
+     */
     public record Settings(String host, int port, String hostname, long maxMessageBytes, boolean authWithoutTls,
-                           Duration idleTimeout) {
+                           Duration idleTimeout, SslContext tls, boolean implicitTls) {
+
+        public Settings(String host, int port, String hostname, long maxMessageBytes, boolean authWithoutTls,
+                        Duration idleTimeout) {
+            this(host, port, hostname, maxMessageBytes, authWithoutTls, idleTimeout, null, false);
+        }
+    }
+
+    /** A line of input and whether it came over TLS. */
+    record Line(byte[] bytes, boolean tls) {
+    }
+
+    /** Marks each line: decoded behind an SslHandler (encrypted) or not. */
+    private static final class LineTagger extends MessageToMessageDecoder<ByteBuf> {
+        @Override
+        protected void decode(ChannelHandlerContext ctx, ByteBuf frame, List<Object> out) {
+            out.add(new Line(ByteBufUtil.getBytes(frame), ctx.pipeline().get(SslHandler.class) != null));
+        }
     }
 
     private final Settings settings;
     private final SmtpBackend backend;
+    private final LoginGuard guard;
     private DisposableServer server;
 
     public SmtpServer(Settings settings, SmtpBackend backend) {
+        this(settings, backend, LoginGuard.disabled());
+    }
+
+    public SmtpServer(Settings settings, SmtpBackend backend, LoginGuard guard) {
         this.settings = settings;
         this.backend = backend;
+        this.guard = guard;
     }
 
     public void start() {
-        server = TcpServer.create()
+        if (settings.implicitTls() && settings.tls() == null) {
+            throw new IllegalStateException("Implicit TLS needs a certificate");
+        }
+        TcpServer tcp = TcpServer.create()
                 .host(settings.host())
                 .port(settings.port())
                 .doOnConnection(connection -> connection
                         .addHandlerFirst("smtp-idle", new ReadTimeoutHandler(settings.idleTimeout().toSeconds(), TimeUnit.SECONDS))
-                        .addHandlerLast("smtp-lines", new LineBasedFrameDecoder(MAX_LINE, true, false)))
+                        .addHandlerLast("smtp-lines", new LineBasedFrameDecoder(MAX_LINE, true, false))
+                        .addHandlerLast("smtp-tag", new LineTagger()));
+        if (settings.implicitTls()) {
+            tcp = tcp.secure(spec -> spec.sslContext(settings.tls()));
+        }
+        server = tcp
                 .handle((inbound, outbound) -> {
+                    Connection[] connection = {null};
                     String[] remoteIp = {"unknown"};
                     inbound.withConnection(c -> {
+                        connection[0] = c;
                         if (c.address() instanceof InetSocketAddress address && address.getAddress() != null) {
                             remoteIp[0] = address.getAddress().getHostAddress();
                         }
                     });
-                    Session session = new Session(remoteIp[0]);
-                    Flux<String> replies = inbound.receive().asByteArray()
+                    Session session = new Session(remoteIp[0], settings.implicitTls());
+                    Flux<String> replies = inbound.receiveObject().cast(Line.class)
                             .concatMap(session::onLine)
                             .onErrorResume(e -> {
                                 log.debug("SMTP {}: connection closed: {}", session.remoteIp, e.toString());
                                 return Mono.just("421 4.4.2 " + settings.hostname() + " closing connection\r\n");
                             })
                             .takeUntil(reply -> session.closing);
-                    return outbound.sendString(Flux.concat(
-                            Mono.just("220 " + settings.hostname() + " ESMTP ready\r\n"), replies), StandardCharsets.US_ASCII);
+                    // One reply at a time, each written before the next line is handled: after "220 Ready to start TLS"
+                    // the TLS handler goes in only when the reply has left in plain text
+                    return Flux.concat(Mono.just("220 " + settings.hostname() + " ESMTP ready\r\n"), replies)
+                            .concatMap(reply -> send(outbound, reply)
+                                    .then(Mono.defer(() -> reply == STARTTLS_READY ? startTls(connection[0], session) : Mono.<Void>empty())))
+                            .then();
                 })
                 .bindNow(Duration.ofSeconds(10));
-        log.info("SMTP server listening on {}:{} ({})", settings.host(), port(), settings.hostname());
+        log.info("SMTP server listening on {}:{} ({}{})", settings.host(), port(), settings.hostname(),
+                settings.implicitTls() ? ", implicit TLS" : settings.tls() != null ? ", STARTTLS" : ", no TLS");
+    }
+
+    private static Mono<Void> send(NettyOutbound outbound, String reply) {
+        return outbound.sendString(Mono.just(reply), StandardCharsets.US_ASCII).then();
+    }
+
+    /** TLS handler in front, fresh line decoder (no plain-text leftovers mixed into encrypted input). */
+    private Mono<Void> startTls(Connection connection, Session session) {
+        ChannelPipeline pipeline = connection.channel().pipeline();
+        SslHandler ssl = settings.tls().newHandler(connection.channel().alloc());
+        pipeline.replace("smtp-lines", "smtp-lines", new LineBasedFrameDecoder(MAX_LINE, true, false));
+        pipeline.addFirst("smtp-tls", ssl);
+        return Mono.create(sink -> ssl.handshakeFuture().addListener(future -> {
+            if (future.isSuccess()) {
+                log.debug("SMTP {}: TLS {}", session.remoteIp, ssl.engine().getSession().getProtocol());
+                sink.success();
+            } else {
+                log.info("SMTP {}: TLS handshake failed: {}", session.remoteIp, future.cause().toString());
+                session.closing = true;
+                connection.dispose();
+                sink.success();
+            }
+        }));
     }
 
     public int port() {
@@ -99,6 +181,7 @@ public class SmtpServer {
 
     private final class Session {
         final String remoteIp;
+        boolean tls;
         State state = State.COMMAND;
         String helo;
         boolean extended;
@@ -109,14 +192,20 @@ public class SmtpServer {
         final ByteArrayOutputStream data = new ByteArrayOutputStream();
         boolean dataTooBig;
         int badCommands;
+        int authFailures;
         volatile boolean closing;
 
-        Session(String remoteIp) {
+        Session(String remoteIp, boolean tls) {
             this.remoteIp = remoteIp;
+            this.tls = tls;
         }
 
-        Mono<String> onLine(byte[] raw) {
-            byte[] line = stripCr(raw);
+        Mono<String> onLine(Line input) {
+            if (tls && !input.tls()) {
+                // Sent in plain text after STARTTLS, before the handshake: never execute it
+                return Mono.error(new IllegalStateException("plain-text input after STARTTLS"));
+            }
+            byte[] line = stripCr(input.bytes());
             return switch (state) {
                 case DATA -> onDataLine(line);
                 case AUTH_PLAIN -> authPlain(ascii(line));
@@ -142,7 +231,7 @@ public class SmtpServer {
                 }
                 case "NOOP" -> reply("250 2.0.0 OK");
                 case "VRFY" -> reply("252 2.5.0 Cannot VRFY user, but will accept message");
-                case "STARTTLS" -> reply("454 4.7.0 TLS not available");
+                case "STARTTLS" -> startTls(arg);
                 case "QUIT" -> {
                     closing = true;
                     yield reply("221 2.0.0 " + settings.hostname() + " Bye");
@@ -167,15 +256,41 @@ public class SmtpServer {
             sb.append("250-SIZE ").append(settings.maxMessageBytes()).append("\r\n");
             sb.append("250-8BITMIME\r\n");
             sb.append("250-PIPELINING\r\n");
-            if (settings.authWithoutTls()) {
+            if (settings.tls() != null && !tls) {
+                sb.append("250-STARTTLS\r\n");
+            }
+            if (authAllowed()) {
                 sb.append("250-AUTH PLAIN LOGIN\r\n");
             }
             sb.append("250 ENHANCEDSTATUSCODES\r\n");
             return Mono.just(sb.toString());
         }
 
+        private boolean authAllowed() {
+            return tls || settings.authWithoutTls();
+        }
+
+        private Mono<String> startTls(String arg) {
+            if (settings.tls() == null) {
+                return reply("454 4.7.0 TLS not available");
+            }
+            if (tls) {
+                return bad("503 5.5.1 TLS already active");
+            }
+            if (!arg.isEmpty()) {
+                return reply("501 5.5.4 Syntax: STARTTLS");
+            }
+            // RFC 3207 4.2: everything known about the client is forgotten, a new EHLO is expected
+            tls = true;
+            helo = null;
+            extended = false;
+            authenticatedUser = null;
+            resetTransaction();
+            return Mono.just(STARTTLS_READY);
+        }
+
         private Mono<String> auth(String arg) {
-            if (!settings.authWithoutTls()) {
+            if (!authAllowed()) {
                 return reply("538 5.7.11 Encryption required for requested authentication mechanism");
             }
             if (helo == null || !extended) {
@@ -251,16 +366,32 @@ public class SmtpServer {
 
         private Mono<String> checkPassword(String user, String password) {
             String username = user.trim().toLowerCase(Locale.ROOT);
+            Duration wait = guard.retryAfter(remoteIp, username);
+            if (!wait.isZero()) {
+                // Blocked: the password is not even checked, the connection is closed
+                log.warn("SMTP {}: login as {} refused, blocked for {}", remoteIp, username, LoginGuard.human(wait));
+                closing = true;
+                return reply("421 4.7.0 Too many failed logins, try again in " + LoginGuard.human(wait));
+            }
             return blocking(() -> backend.authenticate(username, password))
-                    .map(ok -> {
+                    .flatMap(ok -> {
                         if (ok) {
+                            guard.success(remoteIp, username);
                             authenticatedUser = username;
                             log.info("SMTP {}: authenticated as {}", remoteIp, username);
-                            return "235 2.7.0 Authentication successful\r\n";
+                            return Mono.just("235 2.7.0 Authentication successful\r\n");
                         }
+                        guard.failure(remoteIp, username);
                         log.warn("SMTP {}: authentication failed for {}", remoteIp, username);
                         badCommands++;
-                        return "535 5.7.8 Authentication credentials invalid\r\n";
+                        if (++authFailures >= MAX_AUTH_FAILURES) {
+                            closing = true;
+                        }
+                        String answer = closing
+                                ? "535 5.7.8 Authentication credentials invalid, closing connection\r\n"
+                                : "535 5.7.8 Authentication credentials invalid\r\n";
+                        Duration delay = guard.failureDelay();
+                        return delay.isZero() ? Mono.just(answer) : Mono.just(answer).delayElement(delay);
                     });
         }
 
@@ -369,7 +500,7 @@ public class SmtpServer {
 
         private byte[] withReceivedHeader(byte[] message) {
             String received = "Received: from " + helo + " ([" + remoteIp + "])\r\n"
-                    + "\tby " + settings.hostname() + " with " + (authenticatedUser != null ? "ESMTPA" : "ESMTP") + ";\r\n"
+                    + "\tby " + settings.hostname() + " with " + (tls ? "ESMTPS" : "ESMTP") + (authenticatedUser != null ? "A" : "") + ";\r\n"
                     + "\t" + DateTimeFormatter.RFC_1123_DATE_TIME.format(ZonedDateTime.now()) + "\r\n";
             byte[] header = received.getBytes(StandardCharsets.US_ASCII);
             byte[] all = new byte[header.length + message.length];

backend/src/main/java/com/mailserver/smtp/SmtpTls.java

@@ -0,0 +1,114 @@
+package com.mailserver.smtp;
+
+import io.netty.handler.ssl.SslContext;
+import io.netty.handler.ssl.SslContextBuilder;
+import org.bouncycastle.asn1.x500.X500Name;
+import org.bouncycastle.asn1.x509.Extension;
+import org.bouncycastle.asn1.x509.GeneralName;
+import org.bouncycastle.asn1.x509.GeneralNames;
+import org.bouncycastle.cert.jcajce.JcaX509CertificateConverter;
+import org.bouncycastle.cert.jcajce.JcaX509v3CertificateBuilder;
+import org.bouncycastle.operator.jcajce.JcaContentSignerBuilder;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.math.BigInteger;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.attribute.PosixFilePermissions;
+import java.security.KeyPair;
+import java.security.KeyPairGenerator;
+import java.security.SecureRandom;
+import java.security.cert.X509Certificate;
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Base64;
+import java.util.Date;
+
+/**
+ * Certificate for SMTP TLS (STARTTLS and implicit TLS):
+ * <ul>
+ *   <li>{@code cert} and {@code key} given (PEM: certificate chain and the key — PKCS#8, RSA or EC, e.g. from Let's Encrypt) —
+ *       used as is and read again when the files change ({@link ReloadingKeyManager}, checked once a minute);</li>
+ *   <li>otherwise a self-signed certificate for the server hostname, created once in {@code dir} and reused —
+ *       enough for encryption between our own services; other servers deliver over it too (MX delivery does not
+ *       check certificates, RFC 7435 opportunistic TLS).</li>
+ * </ul>
+ */
+public final class SmtpTls {
+
+    private static final Logger log = LoggerFactory.getLogger(SmtpTls.class);
+    static final String CERT_FILE = "smtp-cert.pem";
+    static final String KEY_FILE = "smtp-key.pem";
+    static final Duration RELOAD_CHECK = Duration.ofMinutes(1);
+
+    private SmtpTls() {
+    }
+
+    public static SslContext serverContext(String certFile, String keyFile, Path dir, String hostname) throws Exception {
+        boolean givenCert = certFile != null && !certFile.isBlank();
+        boolean givenKey = keyFile != null && !keyFile.isBlank();
+        if (givenCert != givenKey) {
+            throw new IllegalStateException("TLS: set both the certificate and the key file, or neither");
+        }
+        Path cert;
+        Path key;
+        if (givenCert) {
+            cert = Path.of(certFile);
+            key = Path.of(keyFile);
+            log.info("SMTP TLS: certificate {}", cert);
+        } else {
+            cert = dir.resolve(CERT_FILE);
+            key = dir.resolve(KEY_FILE);
+            if (!Files.exists(cert) || !Files.exists(key)) {
+                selfSigned(hostname, cert, key);
+                log.warn("SMTP TLS: created a self-signed certificate for {} in {}", hostname, dir);
+            } else {
+                log.info("SMTP TLS: self-signed certificate {}", cert);
+            }
+        }
+        // Read again when the files change (a renewed Let's Encrypt certificate) — no restart needed
+        return SslContextBuilder.forServer(new ReloadingKeyManager(cert, key, RELOAD_CHECK, Clock.systemUTC()))
+                .protocols("TLSv1.3", "TLSv1.2")
+                .build();
+    }
+
+    static void selfSigned(String hostname, Path certFile, Path keyFile) throws Exception {
+        KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
+        generator.initialize(2048, new SecureRandom());
+        KeyPair pair = generator.generateKeyPair();
+        X500Name name = new X500Name("CN=" + hostname);
+        Instant now = Instant.now();
+        JcaX509v3CertificateBuilder builder = new JcaX509v3CertificateBuilder(name,
+                new BigInteger(64, new SecureRandom()), Date.from(now.minus(Duration.ofDays(1))),
+                Date.from(now.plus(Duration.ofDays(3650))), name, pair.getPublic());
+        builder.addExtension(Extension.subjectAlternativeName, false,
+                new GeneralNames(new GeneralName(GeneralName.dNSName, hostname)));
+        X509Certificate certificate = new JcaX509CertificateConverter()
+                .getCertificate(builder.build(new JcaContentSignerBuilder("SHA256withRSA").build(pair.getPrivate())));
+
+        Files.createDirectories(keyFile.toAbsolutePath().getParent());
+        write(keyFile, pem("PRIVATE KEY", pair.getPrivate().getEncoded()), true);
+        write(certFile, pem("CERTIFICATE", certificate.getEncoded()), false);
+    }
+
+    private static String pem(String type, byte[] der) {
+        return "-----BEGIN " + type + "-----\n"
+                + Base64.getMimeEncoder(64, new byte[]{'\n'}).encodeToString(der)
+                + "\n-----END " + type + "-----\n";
+    }
+
+    private static void write(Path file, String text, boolean secret) throws IOException {
+        Files.writeString(file, text, StandardCharsets.US_ASCII);
+        if (secret) {
+            try {
+                Files.setPosixFilePermissions(file, PosixFilePermissions.fromString("rw-------"));
+            } catch (UnsupportedOperationException ignored) {
+                // not a POSIX file system
+            }
+        }
+    }
+}

backend/src/main/resources/application.properties

@@ -41,6 +41,13 @@ mailserver.smtp.port=${SMTP_PORT:3025}
 mailserver.smtp.hostname=${MAIL_HOSTNAME:localhost}
 mailserver.smtp.auth-without-tls=${SMTP_AUTH_WITHOUT_TLS:false}
 mailserver.smtp.max-message-bytes=26214400
+# TLS (75.1): STARTTLS on the SMTP port; implicit TLS on SMTPS_PORT (465) if set. Certificate: MAIL_TLS_CERT + MAIL_TLS_KEY
+# (PEM, PKCS#8 key), otherwise a self-signed one created once in MAIL_TLS_DIR. MAIL_TLS=false — no TLS
+mailserver.tls.enabled=${MAIL_TLS:true}
+mailserver.tls.cert-file=${MAIL_TLS_CERT:}
+mailserver.tls.key-file=${MAIL_TLS_KEY:}
+mailserver.tls.dir=${MAIL_TLS_DIR:./tls}
+mailserver.smtps.port=${SMTPS_PORT:0}
 
 # Outbound: off | mx (straight to recipients' MX, port 25) | smarthost (via a provider, e.g. Resend)
 mailserver.outbound.mode=${OUTBOUND_MODE:off}
@@ -50,10 +57,12 @@ mailserver.outbound.username=${OUTBOUND_USERNAME:}
 mailserver.outbound.password=${OUTBOUND_PASSWORD:}
 mailserver.outbound.tls=${OUTBOUND_TLS:starttls}
 
-# IMAP — off: simplified, blocks the event loop (v0.2.3 75.2)
-mailserver.imap.enabled=false
-mailserver.imap.port=1143
-mailserver.imap.hostname=localhost
+# IMAP (75.2): STARTTLS on IMAP_PORT, implicit TLS on IMAPS_PORT (993) if set; same certificate as SMTP.
+# LOGIN only inside TLS unless IMAP_AUTH_WITHOUT_TLS=true (a closed network only)
+mailserver.imap.enabled=${IMAP_ENABLED:true}
+mailserver.imap.port=${IMAP_PORT:3143}
+mailserver.imaps.port=${IMAPS_PORT:0}
+mailserver.imap.auth-without-tls=${IMAP_AUTH_WITHOUT_TLS:false}
 
 # DKIM — signing of our mail; DNS record printed to the log at start
 mailserver.dkim.enabled=${DKIM_ENABLED:true}
@@ -74,3 +83,15 @@ management.endpoints.web.exposure.include=health
 management.endpoint.health.show-details=never
 
 logging.level.com.mailserver=INFO
+
+# Brute-force protection for SMTP AUTH, IMAP login, web login and password change (one counter for all of them):
+# MAX_PER_IP wrong passwords from one IP within WINDOW → the IP is blocked for BLOCK (each next block twice as long,
+# up to MAX_BLOCK); MAX_PER_ACCOUNT wrong passwords to one mailbox from any IPs → the mailbox is blocked for BLOCK,
+# except for IPs that logged in to it before. TRUSTED_IPS (comma-separated) are never blocked by IP
+mailserver.login-guard.enabled=${LOGIN_GUARD:true}
+mailserver.login-guard.max-per-ip=${LOGIN_GUARD_MAX_PER_IP:10}
+mailserver.login-guard.max-per-account=${LOGIN_GUARD_MAX_PER_ACCOUNT:20}
+mailserver.login-guard.window=${LOGIN_GUARD_WINDOW:15m}
+mailserver.login-guard.block=${LOGIN_GUARD_BLOCK:15m}
+mailserver.login-guard.max-block=${LOGIN_GUARD_MAX_BLOCK:24h}
+mailserver.login-guard.trusted-ips=${LOGIN_GUARD_TRUSTED_IPS:}

backend/src/main/resources/db/migration/V4__imap.sql

@@ -0,0 +1,43 @@
+-- IMAP (75.2): UIDs per folder, IMAP flags, the original message text
+
+-- UIDVALIDITY: never changes for a folder; UIDNEXT: the next UID to give out
+ALTER TABLE folders ADD COLUMN uid_validity BIGINT NOT NULL DEFAULT (EXTRACT(EPOCH FROM now())::BIGINT);
+ALTER TABLE folders ADD COLUMN uid_next BIGINT NOT NULL DEFAULT 1;
+
+-- UID inside the folder; strictly increasing — a message moved into a folder gets a new, larger UID
+ALTER TABLE messages ADD COLUMN uid BIGINT;
+ALTER TABLE messages ADD COLUMN is_answered BOOLEAN NOT NULL DEFAULT FALSE;
+ALTER TABLE messages ADD COLUMN is_deleted BOOLEAN NOT NULL DEFAULT FALSE;
+
+UPDATE messages m SET uid = numbered.n
+FROM (SELECT id, ROW_NUMBER() OVER (PARTITION BY folder_id ORDER BY received_at, id) AS n FROM messages) numbered
+WHERE m.id = numbered.id;
+
+UPDATE folders f SET uid_next = COALESCE((SELECT MAX(uid) FROM messages WHERE folder_id = f.id), 0) + 1;
+
+ALTER TABLE messages ALTER COLUMN uid SET NOT NULL;
+CREATE UNIQUE INDEX idx_messages_folder_uid ON messages(folder_id, uid);
+
+-- The UID is given out by the database, so every path that stores or moves a message (SMTP, web client, IMAP)
+-- gets it right without knowing about IMAP
+CREATE FUNCTION assign_message_uid() RETURNS trigger AS $$
+BEGIN
+    UPDATE folders SET uid_next = uid_next + 1 WHERE id = NEW.folder_id RETURNING uid_next - 1 INTO NEW.uid;
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE TRIGGER messages_uid_on_insert BEFORE INSERT ON messages
+    FOR EACH ROW EXECUTE FUNCTION assign_message_uid();
+
+-- The web client saves the whole row (folder_id included) — only a real move gets a new UID
+CREATE TRIGGER messages_uid_on_move BEFORE UPDATE OF folder_id ON messages
+    FOR EACH ROW WHEN (NEW.folder_id IS DISTINCT FROM OLD.folder_id) EXECUTE FUNCTION assign_message_uid();
+
+-- The message exactly as received (SMTP) or appended (IMAP APPEND); for messages without it the server builds
+-- the MIME text once from the stored fields and keeps it here, so sizes and bytes never change between fetches.
+-- Removed when a draft changes.
+CREATE TABLE message_sources (
+    message_id BIGINT PRIMARY KEY REFERENCES messages(id) ON DELETE CASCADE,
+    raw BYTEA NOT NULL
+);

backend/src/test/java/com/mailserver/config/LoginGuardConfigTest.java

@@ -0,0 +1,46 @@
+package com.mailserver.config;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.mock.http.server.reactive.MockServerHttpRequest;
+
+import java.net.InetSocketAddress;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class LoginGuardConfigTest {
+
+    private final LoginGuardConfig.TrustedProxyHeaderTransformer transformer = new LoginGuardConfig.TrustedProxyHeaderTransformer();
+
+    private ServerHttpRequest from(String peer) {
+        return MockServerHttpRequest.post("/api/login")
+                .remoteAddress(new InetSocketAddress(peer, 40000))
+                .header("X-Forwarded-For", "198.51.100.9")
+                .header("X-Forwarded-Proto", "https")
+                .build();
+    }
+
+    @Test
+    void forwardedForIsBelievedFromAPrivateProxy() {
+        ServerHttpRequest request = transformer.apply(from("172.18.0.5"));
+        assertThat(request.getRemoteAddress().getHostString()).isEqualTo("198.51.100.9");
+        assertThat(request.getURI().getScheme()).isEqualTo("https");
+    }
+
+    @Test
+    void forwardedForFromTheInternetIsDropped() {
+        ServerHttpRequest request = transformer.apply(from("203.0.113.7"));
+        assertThat(request.getRemoteAddress().getAddress().getHostAddress()).isEqualTo("203.0.113.7");
+        assertThat(request.getHeaders().containsKey("X-Forwarded-For")).isFalse();
+    }
+
+    @Test
+    void privateRanges() {
+        for (String ip : new String[]{"127.0.0.1", "10.30.0.13", "172.16.0.1", "192.168.1.1", "fd00::1", "::1", "fe80::1"}) {
+            assertThat(LoginGuardConfig.privatePeer(new InetSocketAddress(ip, 1))).as(ip).isTrue();
+        }
+        for (String ip : new String[]{"103.109.235.154", "172.32.0.1", "2001:db8::1", "8.8.8.8"}) {
+            assertThat(LoginGuardConfig.privatePeer(new InetSocketAddress(ip, 1))).as(ip).isFalse();
+        }
+    }
+}

backend/src/test/java/com/mailserver/controller/AuthenticationControllerTest.java

@@ -0,0 +1,81 @@
+package com.mailserver.controller;
+
+import com.mailserver.config.MailDomains;
+import com.mailserver.domain.User;
+import com.mailserver.dto.LoginRequest;
+import com.mailserver.security.LoginGuard;
+import com.mailserver.service.MailService;
+import com.mailserver.service.UserService;
+import com.mailserver.util.JwtUtils;
+import org.junit.jupiter.api.Test;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.mock.http.server.reactive.MockServerHttpRequest;
+import reactor.core.publisher.Mono;
+
+import java.net.InetSocketAddress;
+import java.time.Duration;
+import java.util.Map;
+import java.util.Set;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+class AuthenticationControllerTest {
+
+    private final UserService users = mock(UserService.class);
+    private final JwtUtils jwt = mock(JwtUtils.class);
+    private final LoginGuard guard = new LoginGuard(new LoginGuard.Settings(true, 3, 100, Duration.ofMinutes(15),
+            Duration.ofMinutes(15), Duration.ofHours(24), Duration.ofDays(30), Set.of(), Duration.ZERO));
+    private final AuthenticationController controller = new AuthenticationController(users, mock(MailService.class), jwt,
+            mock(MailDomains.class), false, guard);
+
+    private final User alice = new User();
+
+    AuthenticationControllerTest() {
+        alice.setEmail("alice@x.test");
+        alice.setPassword("hash");
+        when(users.findByEmail("alice@x.test")).thenReturn(Mono.just(alice));
+        when(users.findByEmail("ghost@x.test")).thenReturn(Mono.empty());
+        when(users.checkPassword(eq(alice), anyString())).thenAnswer(i -> "secret".equals(i.getArgument(1)));
+        when(jwt.generateToken(any())).thenReturn("token");
+    }
+
+    private ResponseEntity<?> login(String ip, String email, String password) {
+        LoginRequest request = new LoginRequest();
+        request.setEmail(email);
+        request.setPassword(password);
+        MockServerHttpRequest http = MockServerHttpRequest.post("/api/login")
+                .remoteAddress(new InetSocketAddress(ip, 40000)).build();
+        return controller.login(Mono.just(request), http).block();
+    }
+
+    @Test
+    void unknownMailboxAndWrongPasswordLookTheSameAndBothCount() {
+        assertThat(login("1.2.3.4", "ghost@x.test", "x").getBody()).isEqualTo(Map.of("error", "Invalid credentials"));
+        assertThat(login("1.2.3.4", "alice@x.test", "x").getBody()).isEqualTo(Map.of("error", "Invalid credentials"));
+        login("1.2.3.4", "alice@x.test", "y");
+
+        ResponseEntity<?> blocked = login("1.2.3.4", "alice@x.test", "secret");
+        assertThat(blocked.getStatusCode()).isEqualTo(HttpStatus.TOO_MANY_REQUESTS);
+        assertThat(blocked.getHeaders().getFirst("Retry-After")).isEqualTo("900");
+        assertThat(blocked.getBody()).isEqualTo(Map.of("error", "Too many failed logins, try again in 15 min"));
+
+        assertThat(login("5.6.7.8", "alice@x.test", "secret").getStatusCode()).isEqualTo(HttpStatus.OK);
+    }
+
+    @Test
+    void blockedAttemptDoesNotCheckThePassword() {
+        for (int i = 0; i < 3; i++) {
+            login("1.2.3.4", "ghost@x.test", "x");
+        }
+        login("1.2.3.4", "alice@x.test", "secret");
+        verify(users, never()).checkPassword(any(), eq("secret"));
+    }
+}

backend/src/test/java/com/mailserver/imap/ImapServerTest.java

@@ -0,0 +1,373 @@
+package com.mailserver.imap;
+
+import com.mailserver.smtp.SmtpTls;
+import jakarta.mail.BodyPart;
+import jakarta.mail.Flags;
+import jakarta.mail.Folder;
+import jakarta.mail.Message;
+import jakarta.mail.Multipart;
+import jakarta.mail.Session;
+import jakarta.mail.Store;
+import jakarta.mail.UIDFolder;
+import jakarta.mail.internet.InternetAddress;
+import jakarta.mail.internet.MimeMessage;
+import jakarta.mail.search.SubjectTerm;
+import org.eclipse.angus.mail.imap.AppendUID;
+import org.eclipse.angus.mail.imap.IMAPFolder;
+import com.mailserver.security.LoginGuard;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import javax.net.ssl.SSLContext;
+import javax.net.ssl.SSLSocket;
+import javax.net.ssl.TrustManager;
+import javax.net.ssl.X509TrustManager;
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+import java.io.OutputStream;
+import java.net.Socket;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Path;
+import java.security.cert.X509Certificate;
+import java.time.Duration;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Properties;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class ImapServerTest {
+
+    static final String PLAIN = """
+            From: Bob <bob@elsewhere.test>
+            To: alice@example.test
+            Subject: Hello Alice
+            Date: Thu, 05 Nov 2026 10:00:00 +0000
+            Message-ID: <hello@elsewhere.test>
+            Content-Type: text/plain; charset=utf-8
+
+            Hi there, line one.
+            Line two.
+            """;
+
+    static final String WITH_FILE = """
+            From: =?UTF-8?B?0JDQvdC90LA=?= <anna@elsewhere.test>
+            To: alice@example.test
+            Subject: =?UTF-8?B?0J7RgtGH0ZHRgg==?=
+            Date: Thu, 05 Nov 2026 11:00:00 +0000
+            MIME-Version: 1.0
+            Content-Type: multipart/mixed; boundary="b1"
+
+            preamble
+            --b1
+            Content-Type: text/plain; charset=utf-8
+
+            See the report.
+            --b1
+            Content-Type: application/pdf; name="report.pdf"
+            Content-Disposition: attachment; filename="report.pdf"
+            Content-Transfer-Encoding: base64
+
+            JVBERi0xLjQgdGVzdA==
+            --b1--
+            """;
+
+    @TempDir
+    Path tlsDir;
+
+    private MemoryImapStore store;
+    private ImapServer server;
+
+    @BeforeEach
+    void start() throws Exception {
+        store = new MemoryImapStore();
+        store.deliver("INBOX", PLAIN);
+        store.deliver("INBOX", WITH_FILE);
+        server = new ImapServer(new ImapServer.Settings("127.0.0.1", 0, "mx.example.test", false,
+                SmtpTls.serverContext(null, null, tlsDir, "mx.example.test"), false, 1_000_000,
+                Duration.ofMinutes(5), Duration.ofMillis(200)), store);
+        server.start();
+    }
+
+    @AfterEach
+    void stop() {
+        server.stop();
+    }
+
+    private Store connect() throws Exception {
+        Properties props = new Properties();
+        props.put("mail.imap.host", "127.0.0.1");
+        props.put("mail.imap.port", String.valueOf(server.port()));
+        props.put("mail.imap.starttls.enable", "true");
+        props.put("mail.imap.starttls.required", "true");
+        props.put("mail.imap.ssl.trust", "*");
+        props.put("mail.imap.ssl.checkserveridentity", "false");
+        Store imap = Session.getInstance(props).getStore("imap");
+        imap.connect("alice@example.test", "secret");
+        return imap;
+    }
+
+    @Test
+    void realClientReadsFoldersMessagesAndAttachments() throws Exception {
+        try (Store imap = connect()) {
+            List<String> names = Arrays.stream(imap.getDefaultFolder().list("*")).map(Folder::getFullName).toList();
+            assertThat(names).contains("INBOX", "Drafts", "Sent", "Spam", "Trash");
+
+            IMAPFolder inbox = (IMAPFolder) imap.getFolder("INBOX");
+            inbox.open(Folder.READ_WRITE);
+            assertThat(inbox.getMessageCount()).isEqualTo(2);
+            assertThat(inbox.getUnreadMessageCount()).isEqualTo(2);
+
+            Message first = inbox.getMessage(1);
+            assertThat(first.getSubject()).isEqualTo("Hello Alice");
+            assertThat(((InternetAddress) first.getFrom()[0]).getPersonal()).isEqualTo("Bob");
+            assertThat(first.getContent().toString()).contains("Line two.");
+            assertThat(first.isSet(Flags.Flag.SEEN)).isTrue(); // BODY[] without PEEK
+
+            Message second = inbox.getMessage(2);
+            assertThat(second.getSubject()).isEqualTo("Отчёт");
+            assertThat(((InternetAddress) second.getFrom()[0]).getPersonal()).isEqualTo("Анна");
+            Multipart parts = (Multipart) second.getContent(); // BODYSTRUCTURE, then BODY[1] and BODY[2]
+            assertThat(parts.getCount()).isEqualTo(2);
+            assertThat(parts.getBodyPart(0).getContent().toString()).contains("See the report.");
+            BodyPart file = parts.getBodyPart(1);
+            assertThat(file.getFileName()).isEqualTo("report.pdf");
+            assertThat(new String(file.getInputStream().readAllBytes(), StandardCharsets.US_ASCII)).isEqualTo("%PDF-1.4 test");
+
+            assertThat(inbox.search(new SubjectTerm("hello"))).hasSize(1);
+            assertThat(inbox.getUID(first)).isEqualTo(1);
+            assertThat(inbox.getMessageByUID(2).getSubject()).isEqualTo("Отчёт");
+        }
+    }
+
+    @Test
+    void appendCopyMoveAndExpunge() throws Exception {
+        try (Store imap = connect()) {
+            IMAPFolder sent = (IMAPFolder) imap.getFolder("Sent");
+            MimeMessage outgoing = new MimeMessage(Session.getInstance(new Properties()));
+            outgoing.setFrom(new InternetAddress("alice@example.test"));
+            outgoing.setRecipient(Message.RecipientType.TO, new InternetAddress("bob@elsewhere.test"));
+            outgoing.setSubject("Sent from Thunderbird");
+            outgoing.setText("body");
+            AppendUID[] appended = sent.appendUIDMessages(new Message[]{outgoing});
+            assertThat(appended[0].uid).isEqualTo(1);
+            assertThat(appended[0].uidvalidity).isEqualTo(store.box("Sent").uidValidity());
+
+            IMAPFolder inbox = (IMAPFolder) imap.getFolder("INBOX");
+            inbox.open(Folder.READ_WRITE);
+            inbox.copyMessages(new Message[]{inbox.getMessage(1)}, imap.getFolder("Trash"));
+            inbox.moveMessages(new Message[]{inbox.getMessage(2)}, imap.getFolder("Spam"));
+            inbox.close(false); // JavaMail counts EXPUNGEd messages until the folder is opened again
+            inbox.open(Folder.READ_WRITE);
+            assertThat(inbox.getMessageCount()).isEqualTo(1);
+
+            inbox.getMessage(1).setFlag(Flags.Flag.DELETED, true);
+            inbox.expunge();
+            assertThat(inbox.getMessageCount()).isZero();
+        }
+        assertThat(store.entries(store.box("Trash").id())).hasSize(1);
+        assertThat(store.entries(store.box("Spam").id())).hasSize(1);
+        assertThat(store.entries(store.box("Sent").id())).hasSize(1);
+    }
+
+    @Test
+    void createRenameAndDeleteFolders() throws Exception {
+        try (Store imap = connect()) {
+            Folder projects = imap.getFolder("Проекты");
+            assertThat(projects.create(Folder.HOLDS_MESSAGES)).isTrue();
+            assertThat(Arrays.stream(imap.getDefaultFolder().list("*")).map(Folder::getFullName)).contains("Проекты");
+            assertThat(projects.renameTo(imap.getFolder("Archive"))).isTrue();
+            assertThat(imap.getFolder("Archive").delete(false)).isTrue();
+            assertThat(imap.getFolder("Archive").exists()).isFalse();
+        }
+    }
+
+    @Test
+    void wrongPasswordsCloseTheConnectionAndTheGuardBlocksTheIp() throws Exception {
+        server.stop();
+        LoginGuard guard = new LoginGuard(new LoginGuard.Settings(true, 4, 100, Duration.ofMinutes(15),
+                Duration.ofMinutes(15), Duration.ofHours(24), Duration.ofDays(30), java.util.Set.of(), Duration.ZERO));
+        server = new ImapServer(new ImapServer.Settings("127.0.0.1", 0, "mx.example.test", false,
+                SmtpTls.serverContext(null, null, tlsDir, "mx.example.test"), false, 1_000_000,
+                Duration.ofMinutes(5), Duration.ofMillis(200)), store, guard);
+        server.start();
+        try (Client client = new Client(server.port())) {
+            client.read();
+            client.tls("s");
+            assertThat(client.send("a LOGIN alice@example.test w1")).startsWith("a NO [AUTHENTICATIONFAILED]");
+            assertThat(client.send("b LOGIN alice@example.test w2")).startsWith("b NO [AUTHENTICATIONFAILED]");
+            assertThat(client.untilTagged("c", "c LOGIN alice@example.test w3")).contains("* BYE Too many failed logins");
+            assertThat(client.read()).isNull();
+        }
+        try (Client client = new Client(server.port())) {
+            client.read();
+            client.tls("s");
+            assertThat(client.send("a LOGIN alice@example.test w4")).startsWith("a NO [AUTHENTICATIONFAILED]");
+            assertThat(client.untilTagged("b", "b LOGIN alice@example.test secret"))
+                    .anyMatch(line -> line.startsWith("* BYE Too many failed logins, try again in 15 min"))
+                    .anyMatch(line -> line.startsWith("b NO [UNAVAILABLE]"));
+        }
+    }
+
+    @Test
+    void loginIsRefusedInPlainTextAndTheGreetingSaysSo() throws Exception {
+        try (Client client = new Client(server.port())) {
+            String greeting = client.read();
+            assertThat(greeting).contains("STARTTLS").contains("LOGINDISABLED").doesNotContain("AUTH=PLAIN");
+            assertThat(client.send("a LOGIN alice@example.test secret")).startsWith("a NO [PRIVACYREQUIRED]");
+        }
+    }
+
+    @Test
+    void literalsAndLiteralPlus() throws Exception {
+        try (Client client = new Client(server.port())) {
+            client.read();
+            client.tls("s");
+            client.write("a LOGIN {18}\r\n");
+            assertThat(client.read()).startsWith("+ ");
+            client.write("alice@example.test {6+}\r\nsecret\r\n");
+            assertThat(client.read()).startsWith("a OK");
+            String message = "Subject: via literal+\r\n\r\nhi\r\n";
+            client.write("b APPEND Drafts (\\Seen) {" + message.length() + "+}\r\n" + message + "\r\n");
+            assertThat(client.read()).startsWith("b OK [APPENDUID");
+        }
+        assertThat(store.entries(store.box("Drafts").id())).hasSize(1);
+    }
+
+    @Test
+    void idleReportsNewMailUntilDone() throws Exception {
+        try (Client client = new Client(server.port())) {
+            client.read();
+            client.tls("s");
+            client.send("a LOGIN alice@example.test secret");
+            client.untilTagged("b", "b SELECT INBOX");
+            client.write("c IDLE\r\n");
+            assertThat(client.read()).startsWith("+ idling");
+            store.deliver("INBOX", PLAIN);
+            assertThat(client.read()).isEqualTo("* 3 EXISTS");
+            client.write("DONE\r\n");
+            assertThat(client.read()).startsWith("c OK");
+            assertThat(client.send("d NOOP")).startsWith("d OK");
+        }
+    }
+
+    // CVE-2011-0411 class: commands sent in plain text right after STARTTLS must not run inside TLS
+    @Test
+    void plainTextAfterStartTlsIsNotExecuted() throws Exception {
+        try (Client client = new Client(server.port())) {
+            client.read();
+            client.write("s STARTTLS\r\nx LOGIN alice@example.test secret\r\n");
+            assertThat(client.read()).startsWith("s OK");
+            String reply;
+            try {
+                client.startTls();
+                reply = client.read();
+            } catch (java.io.IOException closed) {
+                reply = null; // the server closed the connection — the expected outcome
+            }
+            assertThat(reply).isNull();
+        }
+    }
+
+    @Test
+    void sectionsOfANestedMessage() {
+        String raw = ("Subject: outer\r\nContent-Type: multipart/mixed; boundary=x\r\n\r\n"
+                + "--x\r\nContent-Type: text/plain\r\n\r\nouter text\r\n"
+                + "--x\r\nContent-Type: message/rfc822\r\n\r\nSubject: inner\r\nContent-Type: text/plain\r\n\r\ninner text\r\n"
+                + "--x--\r\n");
+        MimeTree tree = MimeTree.parse(raw.getBytes(StandardCharsets.US_ASCII));
+        assertThat(text(ImapSession.section(tree, "1"))).isEqualTo("outer text");
+        assertThat(text(ImapSession.section(tree, "2.HEADER"))).isEqualTo("Subject: inner\r\nContent-Type: text/plain\r\n\r\n");
+        assertThat(text(ImapSession.section(tree, "2.TEXT"))).isEqualTo("inner text");
+        assertThat(text(ImapSession.section(tree, "2.1"))).isEqualTo("inner text");
+        assertThat(text(ImapSession.section(tree, "1.MIME"))).isEqualTo("Content-Type: text/plain\r\n\r\n");
+        assertThat(text(ImapSession.section(tree, "HEADER.FIELDS (SUBJECT)"))).isEqualTo("Subject: outer\r\n\r\n");
+        assertThat(text(ImapSession.section(tree, ""))).isEqualTo(raw);
+    }
+
+    @Test
+    void mailboxNamesUseModifiedUtf7() {
+        // the example of RFC 3501 5.1.3
+        assertThat(ImapWriter.encodeMailbox("~peter/mail/台北/日本語")).isEqualTo("~peter/mail/&U,BTFw-/&ZeVnLIqe-");
+        assertThat(ImapWriter.decodeMailbox("~peter/mail/&U,BTFw-/&ZeVnLIqe-")).isEqualTo("~peter/mail/台北/日本語");
+        assertThat(ImapWriter.decodeMailbox(ImapWriter.encodeMailbox("Проекты & план"))).isEqualTo("Проекты & план");
+    }
+
+    private static String text(byte[] bytes) {
+        return new String(bytes, StandardCharsets.UTF_8);
+    }
+
+    /** Line-oriented IMAP test client. */
+    static final class Client implements AutoCloseable {
+        private Socket socket;
+        private BufferedReader in;
+        private OutputStream out;
+
+        Client(int port) throws Exception {
+            socket = new Socket("127.0.0.1", port);
+            socket.setSoTimeout(5000);
+            in = new BufferedReader(new InputStreamReader(socket.getInputStream(), StandardCharsets.UTF_8));
+            out = socket.getOutputStream();
+        }
+
+        void write(String text) throws Exception {
+            out.write(text.getBytes(StandardCharsets.UTF_8));
+            out.flush();
+        }
+
+        String read() throws Exception {
+            return in.readLine();
+        }
+
+        String send(String line) throws Exception {
+            write(line + "\r\n");
+            return read();
+        }
+
+        /** Sends a command, returns all lines up to its tagged response. */
+        List<String> untilTagged(String tag, String line) throws Exception {
+            write(line + "\r\n");
+            List<String> lines = new ArrayList<>();
+            String next;
+            do {
+                next = read();
+                lines.add(next);
+            } while (next != null && !next.startsWith(tag + " "));
+            return lines;
+        }
+
+        void tls(String tag) throws Exception {
+            assertThat(send(tag + " STARTTLS")).startsWith(tag + " OK");
+            startTls();
+        }
+
+        void startTls() throws Exception {
+            SSLContext context = SSLContext.getInstance("TLS");
+            context.init(null, new TrustManager[]{new X509TrustManager() {
+                public void checkClientTrusted(X509Certificate[] chain, String authType) {
+                }
+
+                public void checkServerTrusted(X509Certificate[] chain, String authType) {
+                }
+
+                public X509Certificate[] getAcceptedIssuers() {
+                    return new X509Certificate[0];
+                }
+            }}, null);
+            SSLSocket ssl = (SSLSocket) context.getSocketFactory().createSocket(socket, "127.0.0.1", socket.getPort(), true);
+            ssl.setUseClientMode(true);
+            ssl.startHandshake();
+            socket = ssl;
+            in = new BufferedReader(new InputStreamReader(ssl.getInputStream(), StandardCharsets.UTF_8));
+            out = ssl.getOutputStream();
+        }
+
+        @Override
+        public void close() throws Exception {
+            socket.close();
+        }
+    }
+}

backend/src/test/java/com/mailserver/imap/MemoryImapStore.java

@@ -0,0 +1,172 @@
+package com.mailserver.imap;
+
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.atomic.AtomicLong;
+
+/** In-memory {@link ImapStore}: one user alice@example.test / secret with the system folders. */
+class MemoryImapStore implements ImapStore {
+
+    static final class Stored {
+        final long id;
+        volatile long folderId;
+        volatile long uid;
+        volatile boolean seen;
+        volatile boolean flagged;
+        volatile boolean answered;
+        volatile boolean deleted;
+        final Instant date;
+        final byte[] raw;
+
+        Stored(long id, long folderId, long uid, byte[] raw, Instant date) {
+            this.id = id;
+            this.folderId = folderId;
+            this.uid = uid;
+            this.raw = raw;
+            this.date = date;
+        }
+
+        Entry entry() {
+            return new Entry(id, uid, seen, flagged, answered, deleted, date);
+        }
+    }
+
+    private final AtomicLong ids = new AtomicLong(100);
+    final List<Mailbox> boxes = new CopyOnWriteArrayList<>();
+    final Map<Long, Long> uidNext = new ConcurrentHashMap<>();
+    final List<Stored> messages = new CopyOnWriteArrayList<>();
+
+    MemoryImapStore() {
+        for (String name : List.of("INBOX", "Drafts", "Sent", "Spam", "Trash")) {
+            addBox(name, true);
+        }
+    }
+
+    private Mailbox addBox(String name, boolean system) {
+        long id = ids.incrementAndGet();
+        uidNext.put(id, 1L);
+        Mailbox box = new Mailbox(id, name, system, 1700000000L + id, 1);
+        boxes.add(box);
+        return box;
+    }
+
+    Mailbox box(String name) {
+        return boxes.stream().filter(b -> b.name().equals(name)).findFirst().orElseThrow();
+    }
+
+    /** Delivers a message into a folder, as SMTP would. */
+    synchronized Stored deliver(String folder, String raw) {
+        Mailbox box = box(folder);
+        Stored stored = new Stored(ids.incrementAndGet(), box.id(), nextUid(box.id()),
+                raw.replace("\n", "\r\n").replace("\r\r\n", "\r\n").getBytes(), Instant.parse("2026-11-05T10:00:00Z"));
+        messages.add(stored);
+        return stored;
+    }
+
+    private synchronized long nextUid(long folderId) {
+        long uid = uidNext.get(folderId);
+        uidNext.put(folderId, uid + 1);
+        return uid;
+    }
+
+    @Override
+    public Account authenticate(String username, String password) {
+        return "alice@example.test".equalsIgnoreCase(username) && "secret".equals(password)
+                ? new Account(1, "alice@example.test") : null;
+    }
+
+    @Override
+    public List<Mailbox> mailboxes(long userId) {
+        return boxes.stream().map(b -> new Mailbox(b.id(), b.name(), b.system(), b.uidValidity(), uidNext.get(b.id()))).toList();
+    }
+
+    @Override
+    public synchronized Mailbox create(long userId, String name) {
+        return addBox(name, false);
+    }
+
+    @Override
+    public synchronized void rename(long userId, Mailbox mailbox, String newName) {
+        boxes.removeIf(b -> b.id() == mailbox.id());
+        boxes.add(new Mailbox(mailbox.id(), newName, false, mailbox.uidValidity(), mailbox.uidNext()));
+    }
+
+    @Override
+    public synchronized void delete(long userId, Mailbox mailbox) {
+        Mailbox trash = box("Trash");
+        move(userId, entries(mailbox.id()), trash);
+        boxes.removeIf(b -> b.id() == mailbox.id());
+    }
+
+    @Override
+    public List<Entry> entries(long folderId) {
+        return messages.stream().filter(m -> m.folderId == folderId)
+                .sorted((a, b) -> Long.compare(a.uid, b.uid)).map(Stored::entry).toList();
+    }
+
+    @Override
+    public byte[] source(long messageId) {
+        return find(messageId).raw;
+    }
+
+    private Stored find(long id) {
+        return messages.stream().filter(m -> m.id == id).findFirst().orElseThrow();
+    }
+
+    @Override
+    public void setFlags(long messageId, boolean seen, boolean flagged, boolean answered, boolean deleted) {
+        Stored m = find(messageId);
+        m.seen = seen;
+        m.flagged = flagged;
+        m.answered = answered;
+        m.deleted = deleted;
+    }
+
+    @Override
+    public synchronized long append(long userId, Mailbox target, byte[] raw, boolean seen, boolean flagged,
+                                    boolean answered, boolean deleted, Instant internalDate) {
+        Stored stored = new Stored(ids.incrementAndGet(), target.id(), nextUid(target.id()), raw,
+                internalDate == null ? Instant.now() : internalDate);
+        stored.seen = seen;
+        stored.flagged = flagged;
+        stored.answered = answered;
+        stored.deleted = deleted;
+        messages.add(stored);
+        return stored.uid;
+    }
+
+    @Override
+    public synchronized List<Long> copy(long userId, List<Entry> list, Mailbox target) {
+        List<Long> uids = new ArrayList<>();
+        for (Entry entry : list) {
+            Stored from = find(entry.id());
+            Stored copy = new Stored(ids.incrementAndGet(), target.id(), nextUid(target.id()), from.raw, from.date);
+            copy.seen = from.seen;
+            copy.flagged = from.flagged;
+            messages.add(copy);
+            uids.add(copy.uid);
+        }
+        return uids;
+    }
+
+    @Override
+    public synchronized List<Long> move(long userId, List<Entry> list, Mailbox target) {
+        List<Long> uids = new ArrayList<>();
+        for (Entry entry : list) {
+            Stored m = find(entry.id());
+            m.folderId = target.id();
+            m.uid = nextUid(target.id());
+            uids.add(m.uid);
+        }
+        return uids;
+    }
+
+    @Override
+    public void expunge(List<Long> messageIds) {
+        messages.removeIf(m -> messageIds.contains(m.id));
+    }
+}

backend/src/test/java/com/mailserver/security/LoginGuardTest.java

@@ -0,0 +1,164 @@
+package com.mailserver.security;
+
+import org.junit.jupiter.api.Test;
+
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.time.ZoneOffset;
+import java.util.Set;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class LoginGuardTest {
+
+    /** Clock the test moves by hand. */
+    static final class TestClock extends Clock {
+        Instant now = Instant.parse("2026-11-06T12:00:00Z");
+
+        void plus(Duration d) {
+            now = now.plus(d);
+        }
+
+        @Override
+        public ZoneOffset getZone() {
+            return ZoneOffset.UTC;
+        }
+
+        @Override
+        public Clock withZone(java.time.ZoneId zone) {
+            return this;
+        }
+
+        @Override
+        public Instant instant() {
+            return now;
+        }
+    }
+
+    private final TestClock clock = new TestClock();
+
+    private LoginGuard guard(int perIp, int perAccount, String... trusted) {
+        return new LoginGuard(new LoginGuard.Settings(true, perIp, perAccount, Duration.ofMinutes(15),
+                Duration.ofMinutes(15), Duration.ofHours(24), Duration.ofDays(30), Set.of(trusted), Duration.ZERO), clock);
+    }
+
+    @Test
+    void ipIsBlockedAfterTheLimitWhateverMailboxItTries() {
+        LoginGuard guard = guard(3, 100);
+        for (int i = 0; i < 2; i++) {
+            guard.failure("1.2.3.4", "user" + i + "@x.test");
+        }
+        assertThat(guard.blocked("1.2.3.4", "any@x.test")).isFalse();
+        guard.failure("1.2.3.4", "user9@x.test");
+        assertThat(guard.retryAfter("1.2.3.4", "any@x.test")).isEqualTo(Duration.ofMinutes(15));
+        assertThat(guard.blocked("5.6.7.8", "any@x.test")).isFalse();
+
+        clock.plus(Duration.ofMinutes(15));
+        assertThat(guard.blocked("1.2.3.4", "any@x.test")).isFalse();
+    }
+
+    @Test
+    void failuresOutsideTheWindowDoNotCount() {
+        LoginGuard guard = guard(3, 100);
+        guard.failure("1.2.3.4", "a@x.test");
+        guard.failure("1.2.3.4", "a@x.test");
+        clock.plus(Duration.ofMinutes(16));
+        guard.failure("1.2.3.4", "a@x.test");
+        assertThat(guard.blocked("1.2.3.4", "a@x.test")).isFalse();
+    }
+
+    @Test
+    void eachNextBlockOfTheSameIpIsTwiceAsLongUpToTheMaximum() {
+        LoginGuard guard = guard(2, 100);
+        Duration expected = Duration.ofMinutes(15);
+        for (int round = 0; round < 10; round++) {
+            guard.failure("1.2.3.4", "a@x.test");
+            guard.failure("1.2.3.4", "a@x.test");
+            Duration wait = guard.retryAfter("1.2.3.4", "b@x.test");
+            assertThat(wait).isEqualTo(expected);
+            clock.plus(wait);
+            expected = expected.multipliedBy(2).compareTo(Duration.ofHours(24)) > 0 ? Duration.ofHours(24) : expected.multipliedBy(2);
+        }
+        // a quiet day forgives
+        clock.plus(Duration.ofHours(25));
+        guard.failure("1.2.3.4", "a@x.test");
+        guard.failure("1.2.3.4", "a@x.test");
+        assertThat(guard.retryAfter("1.2.3.4", "b@x.test")).isEqualTo(Duration.ofMinutes(15));
+    }
+
+    @Test
+    void attemptsWhileBlockedDoNotProlongTheBlock() {
+        LoginGuard guard = guard(2, 100);
+        guard.failure("1.2.3.4", "a@x.test");
+        guard.failure("1.2.3.4", "a@x.test");
+        clock.plus(Duration.ofMinutes(10));
+        guard.failure("1.2.3.4", "a@x.test");
+        assertThat(guard.retryAfter("1.2.3.4", "a@x.test")).isEqualTo(Duration.ofMinutes(5));
+    }
+
+    @Test
+    void distributedAttackBlocksTheMailboxButNotItsOwnerFromAKnownIp() {
+        LoginGuard guard = guard(100, 5);
+        guard.success("10.0.0.7", "Alice@X.test");
+        for (int i = 0; i < 5; i++) {
+            guard.failure("203.0.113." + i, "alice@x.test");
+        }
+        assertThat(guard.blocked("198.51.100.1", "alice@x.test")).isTrue();
+        assertThat(guard.blocked("198.51.100.1", "bob@x.test")).isFalse();
+        assertThat(guard.blocked("10.0.0.7", "alice@x.test")).isFalse();
+    }
+
+    @Test
+    void successForgivesTheIpFailuresButNotAnActiveBlock() {
+        LoginGuard guard = guard(3, 100);
+        guard.failure("1.2.3.4", "a@x.test");
+        guard.failure("1.2.3.4", "a@x.test");
+        guard.success("1.2.3.4", "a@x.test");
+        guard.failure("1.2.3.4", "a@x.test");
+        guard.failure("1.2.3.4", "a@x.test");
+        assertThat(guard.blocked("1.2.3.4", "a@x.test")).isFalse();
+        guard.failure("1.2.3.4", "a@x.test");
+        assertThat(guard.blocked("1.2.3.4", "a@x.test")).isTrue();
+        guard.success("1.2.3.4", "a@x.test");
+        assertThat(guard.blocked("1.2.3.4", "other@x.test")).isTrue();
+    }
+
+    @Test
+    void trustedIpIsNeverBlockedByIp() {
+        LoginGuard guard = guard(2, 100, "172.18.0.1");
+        for (int i = 0; i < 10; i++) {
+            guard.failure("172.18.0.1", "u" + i + "@x.test");
+        }
+        assertThat(guard.blocked("172.18.0.1", "new@x.test")).isFalse();
+    }
+
+    @Test
+    void sweepForgetsOldKeys() {
+        LoginGuard guard = guard(5, 5);
+        guard.failure("1.2.3.4", "a@x.test");
+        assertThat(guard.trackedIps()).isEqualTo(1);
+        assertThat(guard.trackedAccounts()).isEqualTo(1);
+        clock.plus(Duration.ofHours(25).plusMinutes(16));
+        guard.sweep();
+        assertThat(guard.trackedIps()).isZero();
+        assertThat(guard.trackedAccounts()).isZero();
+    }
+
+    @Test
+    void disabledGuardNeverBlocks() {
+        LoginGuard guard = LoginGuard.disabled();
+        for (int i = 0; i < 100; i++) {
+            guard.failure("1.2.3.4", "a@x.test");
+        }
+        assertThat(guard.blocked("1.2.3.4", "a@x.test")).isFalse();
+        assertThat(guard.failureDelay()).isZero();
+    }
+
+    @Test
+    void humanDuration() {
+        assertThat(LoginGuard.human(Duration.ofSeconds(30))).isEqualTo("1 min");
+        assertThat(LoginGuard.human(Duration.ofMinutes(15))).isEqualTo("15 min");
+        assertThat(LoginGuard.human(Duration.ofHours(4))).isEqualTo("4 h");
+    }
+}

backend/src/test/java/com/mailserver/smtp/ReloadingKeyManagerTest.java

@@ -0,0 +1,149 @@
+package com.mailserver.smtp;
+
+import org.bouncycastle.asn1.x500.X500Name;
+import org.bouncycastle.cert.jcajce.JcaX509CertificateConverter;
+import org.bouncycastle.cert.jcajce.JcaX509v3CertificateBuilder;
+import org.bouncycastle.openssl.jcajce.JcaPEMWriter;
+import org.bouncycastle.operator.jcajce.JcaContentSignerBuilder;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.StringWriter;
+import java.math.BigInteger;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.attribute.FileTime;
+import java.security.KeyPair;
+import java.security.KeyPairGenerator;
+import java.security.cert.X509Certificate;
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.time.ZoneOffset;
+import java.util.Date;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class ReloadingKeyManagerTest {
+
+    /** A clock moved by hand */
+    static final class TestClock extends Clock {
+        Instant now = Instant.parse("2026-11-06T12:00:00Z");
+
+        @Override
+        public ZoneOffset getZone() {
+            return ZoneOffset.UTC;
+        }
+
+        @Override
+        public Clock withZone(java.time.ZoneId zone) {
+            return this;
+        }
+
+        @Override
+        public Instant instant() {
+            return now;
+        }
+    }
+
+    @Test
+    void readsTheFilesAgainWhenTheyChange(@TempDir Path dir) throws Exception {
+        Path cert = dir.resolve("cert.pem");
+        Path key = dir.resolve("key.pem");
+        SmtpTls.selfSigned("old.example", cert, key);
+        TestClock clock = new TestClock();
+        ReloadingKeyManager manager = new ReloadingKeyManager(cert, key, Duration.ofMinutes(1), clock);
+
+        String first = manager.chooseEngineServerAlias("RSA", null, null);
+        assertEquals("CN=old.example", subject(manager.getCertificateChain(first)));
+        assertNull(manager.chooseEngineServerAlias("EC", null, null), "an RSA key is not offered for EC");
+
+        SmtpTls.selfSigned("new.example", cert, key);
+        Files.setLastModifiedTime(cert, FileTime.from(Instant.now().plusSeconds(5)));
+        Files.setLastModifiedTime(key, FileTime.from(Instant.now().plusSeconds(5)));
+
+        assertEquals(first, manager.chooseEngineServerAlias("RSA", null, null), "not checked before the interval");
+
+        clock.now = clock.now.plus(Duration.ofMinutes(1));
+        String second = manager.chooseEngineServerAlias("RSA", null, null);
+        assertNotEquals(first, second);
+        assertEquals("CN=new.example", subject(manager.getCertificateChain(second)));
+        assertNotNull(manager.getPrivateKey(second));
+        assertNotNull(manager.getCertificateChain(first), "a handshake that holds the previous alias still finishes");
+    }
+
+    @Test
+    void keepsTheOldCertificateWhenTheNewFileIsBroken(@TempDir Path dir) throws Exception {
+        Path cert = dir.resolve("cert.pem");
+        Path key = dir.resolve("key.pem");
+        SmtpTls.selfSigned("old.example", cert, key);
+        TestClock clock = new TestClock();
+        ReloadingKeyManager manager = new ReloadingKeyManager(cert, key, Duration.ofMinutes(1), clock);
+
+        Files.writeString(cert, "-----BEGIN CERTIFICATE-----\nhalf");
+        Files.setLastModifiedTime(cert, FileTime.from(Instant.now().plusSeconds(5)));
+        clock.now = clock.now.plus(Duration.ofMinutes(2));
+
+        String alias = manager.chooseEngineServerAlias("RSA", null, null);
+        assertEquals("CN=old.example", subject(manager.getCertificateChain(alias)));
+    }
+
+    @Test
+    void readsTraditionalEcKeysAsLegoWritesThem(@TempDir Path dir) throws Exception {
+        KeyPairGenerator generator = KeyPairGenerator.getInstance("EC");
+        generator.initialize(256);
+        KeyPair pair = generator.generateKeyPair();
+        X500Name name = new X500Name("CN=mail.example");
+        X509Certificate certificate = new JcaX509CertificateConverter().getCertificate(
+                new JcaX509v3CertificateBuilder(name, BigInteger.ONE, new Date(System.currentTimeMillis() - 86_400_000L),
+                        new Date(System.currentTimeMillis() + 86_400_000L), name, pair.getPublic())
+                        .build(new JcaContentSignerBuilder("SHA256withECDSA").build(pair.getPrivate())));
+        Path cert = dir.resolve("cert.pem");
+        Path key = dir.resolve("key.pem");
+        Files.writeString(cert, pem(certificate));
+        Files.writeString(key, sec1(pair)); // -----BEGIN EC PRIVATE KEY----- (SEC1 with the curve), not PKCS#8
+        assertTrue(Files.readString(key).contains("EC PRIVATE KEY"));
+
+        ReloadingKeyManager manager = new ReloadingKeyManager(cert, key, Duration.ofMinutes(1), new TestClock());
+        String alias = manager.chooseEngineServerAlias("EC", null, null);
+        assertNotNull(alias);
+        assertEquals("EC", manager.getPrivateKey(alias).getAlgorithm());
+        assertNull(manager.chooseEngineServerAlias("RSA", null, null));
+    }
+
+    @Test
+    void refusesAKeyThatDoesNotMatchTheCertificateType(@TempDir Path dir) throws Exception {
+        Path cert = dir.resolve("cert.pem");
+        Path key = dir.resolve("key.pem");
+        SmtpTls.selfSigned("rsa.example", cert, key);
+        KeyPairGenerator generator = KeyPairGenerator.getInstance("EC");
+        generator.initialize(256);
+        Files.writeString(key, sec1(generator.generateKeyPair()));
+        assertThrows(IllegalStateException.class,
+                () -> new ReloadingKeyManager(cert, key, Duration.ofMinutes(1), new TestClock()));
+    }
+
+    /** As lego and openssl ecparam -genkey write it: SEC1 with the named curve secp256r1 */
+    private static String sec1(KeyPair pair) throws Exception {
+        java.security.interfaces.ECPrivateKey key = (java.security.interfaces.ECPrivateKey) pair.getPrivate();
+        org.bouncycastle.asn1.sec.ECPrivateKey sec1 = new org.bouncycastle.asn1.sec.ECPrivateKey(256, key.getS(),
+                new org.bouncycastle.asn1.x9.X962Parameters(org.bouncycastle.asn1.sec.SECObjectIdentifiers.secp256r1));
+        StringWriter out = new StringWriter();
+        try (org.bouncycastle.util.io.pem.PemWriter writer = new org.bouncycastle.util.io.pem.PemWriter(out)) {
+            writer.writeObject(new org.bouncycastle.util.io.pem.PemObject("EC PRIVATE KEY", sec1.getEncoded()));
+        }
+        return out.toString();
+    }
+
+    private static String subject(X509Certificate[] chain) {
+        return chain[0].getSubjectX500Principal().getName();
+    }
+
+    private static String pem(Object object) throws Exception {
+        StringWriter out = new StringWriter();
+        try (JcaPEMWriter writer = new JcaPEMWriter(out)) {
+            writer.writeObject(object);
+        }
+        return out.toString();
+    }
+}

backend/src/test/java/com/mailserver/smtp/SmtpServerTest.java

@@ -5,14 +5,22 @@ import jakarta.mail.Session;
 import jakarta.mail.Transport;
 import jakarta.mail.internet.InternetAddress;
 import jakarta.mail.internet.MimeMessage;
+import com.mailserver.security.LoginGuard;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
 
 import java.io.BufferedReader;
 import java.io.InputStreamReader;
 import java.io.OutputStream;
 import java.net.Socket;
+import java.nio.file.Path;
+import java.security.cert.X509Certificate;
+import javax.net.ssl.SSLContext;
+import javax.net.ssl.SSLSocket;
+import javax.net.ssl.TrustManager;
+import javax.net.ssl.X509TrustManager;
 import java.nio.charset.StandardCharsets;
 import java.time.Duration;
 import java.util.ArrayList;
@@ -151,6 +159,34 @@ class SmtpServerTest {
         assertThat(backend.messages.get(0)).contains("with ESMTPA;");
     }
 
+    @Test
+    void threeWrongPasswordsCloseTheConnectionAndTheGuardBlocksTheIp() throws Exception {
+        server.stop();
+        LoginGuard guard = new LoginGuard(new LoginGuard.Settings(true, 4, 100, Duration.ofMinutes(15),
+                Duration.ofMinutes(15), Duration.ofHours(24), Duration.ofDays(30), java.util.Set.of(), Duration.ZERO));
+        server = new SmtpServer(new SmtpServer.Settings("127.0.0.1", 0, "mx.example.test", 2000, true,
+                Duration.ofSeconds(30)), backend, guard);
+        server.start();
+        try (Client client = new Client(server.port())) {
+            client.read();
+            client.send("EHLO laptop");
+            client.readReplyLines();
+            assertThat(client.send("AUTH PLAIN " + b64("\0alice@example.test\0w1"))).startsWith("535");
+            assertThat(client.send("AUTH PLAIN " + b64("\0alice@example.test\0w2"))).startsWith("535");
+            assertThat(client.send("AUTH PLAIN " + b64("\0alice@example.test\0w3"))).startsWith("535").contains("closing");
+            assertThat(client.read()).isNull();
+        }
+        try (Client client = new Client(server.port())) {
+            client.read();
+            client.send("EHLO laptop");
+            client.readReplyLines();
+            assertThat(client.send("AUTH PLAIN " + b64("\0bob@example.test\0w4"))).startsWith("535");
+            // 4th failure from 127.0.0.1: blocked — even the right password is not checked
+            assertThat(client.send("AUTH PLAIN " + b64("\0alice@example.test\0secret"))).startsWith("421 4.7.0");
+            assertThat(client.read()).isNull();
+        }
+    }
+
     @Test
     void authLoginWorksToo() throws Exception {
         try (Client client = new Client(server.port())) {
@@ -214,15 +250,131 @@ class SmtpServerTest {
         assertThat(SmtpServer.path("<a b@c>")).isNull();
     }
 
+    // ---------- TLS (75.1) ----------
+
+    @TempDir
+    Path tlsDir;
+
+    private SmtpServer tlsServer(boolean implicit) throws Exception {
+        server.stop();
+        server = new SmtpServer(new SmtpServer.Settings("127.0.0.1", 0, "mx.example.test", 2000, false,
+                Duration.ofSeconds(30), SmtpTls.serverContext(null, null, tlsDir, "mx.example.test"), implicit), backend);
+        server.start();
+        return server;
+    }
+
+    @Test
+    void startTlsThenAuthAndTheSessionStartsOver() throws Exception {
+        tlsServer(false);
+        try (Client client = new Client(server.port())) {
+            client.read();
+            client.send("EHLO laptop");
+            List<String> plain = client.readReplyLines();
+            assertThat(plain).contains("250-STARTTLS").noneMatch(line -> line.contains("AUTH"));
+            assertThat(client.send("AUTH PLAIN " + b64("\0alice@example.test\0secret"))).startsWith("538");
+            assertThat(client.send("MAIL FROM:<x@elsewhere.test>")).startsWith("250");
+
+            assertThat(client.send("STARTTLS")).isEqualTo("220 2.0.0 Ready to start TLS");
+            client.startTls();
+
+            // RFC 3207: MAIL FROM before STARTTLS is forgotten, EHLO again
+            assertThat(client.send("MAIL FROM:<x@elsewhere.test>")).startsWith("503");
+            client.send("EHLO laptop");
+            List<String> secure = client.readReplyLines();
+            assertThat(secure).contains("250-AUTH PLAIN LOGIN").noneMatch(line -> line.contains("STARTTLS"));
+            assertThat(client.send("STARTTLS")).startsWith("503");
+            assertThat(client.send("AUTH PLAIN " + b64("\0alice@example.test\0secret"))).startsWith("235");
+            client.send("MAIL FROM:<alice@example.test>");
+            client.send("RCPT TO:<friend@gmail.com>");
+            client.send("DATA");
+            assertThat(client.send("Subject: tls\r\n\r\nhi\r\n.")).startsWith("250");
+        }
+        assertThat(backend.messages.get(0)).contains("with ESMTPSA;");
+    }
+
+    // CVE-2011-0411: commands sent in plain text right after STARTTLS must not run inside the TLS session
+    @Test
+    void plainTextInjectedAfterStartTlsIsNotExecuted() throws Exception {
+        tlsServer(false);
+        try (Client client = new Client(server.port())) {
+            client.read();
+            client.send("EHLO laptop");
+            client.readReplyLines();
+            client.write("STARTTLS\r\nMAIL FROM:<x@elsewhere.test>\r\nRCPT TO:<bob@example.test>\r\n");
+            assertThat(client.read()).isEqualTo("220 2.0.0 Ready to start TLS");
+            client.startTls();
+            String reply = client.read();
+            assertThat(reply == null || reply.startsWith("421")).as(reply).isTrue();
+        }
+        assertThat(backend.envelopes).isEmpty();
+    }
+
+    @Test
+    void realClientRequiringStartTlsDelivers() throws Exception {
+        tlsServer(false);
+        Properties props = new Properties();
+        props.put("mail.smtp.host", "127.0.0.1");
+        props.put("mail.smtp.port", String.valueOf(server.port()));
+        props.put("mail.smtp.starttls.enable", "true");
+        props.put("mail.smtp.starttls.required", "true");
+        props.put("mail.smtp.ssl.trust", "*");
+        props.put("mail.smtp.ssl.checkserveridentity", "false"); // self-signed for mx.example.test, connecting to 127.0.0.1
+        props.put("mail.smtp.auth", "true");
+        Session session = Session.getInstance(props);
+        MimeMessage message = new MimeMessage(session);
+        message.setFrom(new InternetAddress("alice@example.test"));
+        message.setRecipient(Message.RecipientType.TO, new InternetAddress("bob@example.test"));
+        message.setSubject("Over STARTTLS");
+        message.setText("hello");
+
+        Transport.send(message, "alice@example.test", "secret");
+
+        assertThat(backend.envelopes).hasSize(1);
+        assertThat(backend.envelopes.get(0).authenticatedUser()).isEqualTo("alice@example.test");
+        assertThat(backend.messages.get(0)).contains("with ESMTPSA;");
+    }
+
+    @Test
+    void implicitTlsPortWorksWithoutStartTls() throws Exception {
+        tlsServer(true);
+        Properties props = new Properties();
+        props.put("mail.smtp.host", "127.0.0.1");
+        props.put("mail.smtp.port", String.valueOf(server.port()));
+        props.put("mail.smtp.ssl.enable", "true");
+        props.put("mail.smtp.ssl.trust", "*");
+        props.put("mail.smtp.ssl.checkserveridentity", "false"); // self-signed for mx.example.test, connecting to 127.0.0.1
+        props.put("mail.smtp.auth", "true");
+        Session session = Session.getInstance(props);
+        MimeMessage message = new MimeMessage(session);
+        message.setFrom(new InternetAddress("alice@example.test"));
+        message.setRecipient(Message.RecipientType.TO, new InternetAddress("bob@example.test"));
+        message.setSubject("Over 465");
+        message.setText("hello");
+
+        Transport.send(message, "alice@example.test", "secret");
+
+        assertThat(backend.messages.get(0)).contains("with ESMTPSA;");
+    }
+
+    @Test
+    void selfSignedCertificateIsCreatedOnceAndReused() throws Exception {
+        SmtpTls.serverContext(null, null, tlsDir, "mx.example.test");
+        String first = java.nio.file.Files.readString(tlsDir.resolve(SmtpTls.CERT_FILE));
+        SmtpTls.serverContext(null, null, tlsDir, "mx.example.test");
+
+        assertThat(java.nio.file.Files.readString(tlsDir.resolve(SmtpTls.CERT_FILE))).isEqualTo(first);
+        assertThat(java.nio.file.Files.readString(tlsDir.resolve(SmtpTls.KEY_FILE))).startsWith("-----BEGIN PRIVATE KEY-----");
+    }
+
     private static String b64(String text) {
         return Base64.getEncoder().encodeToString(text.getBytes(StandardCharsets.UTF_8));
     }
 
     /** Line-oriented test client. */
     static final class Client implements AutoCloseable {
-        private final Socket socket;
-        private final BufferedReader in;
-        private final OutputStream out;
+        private Socket socket;
+        private BufferedReader in;
+        private OutputStream out;
 
         Client(int port) throws Exception {
             socket = new Socket("127.0.0.1", port);
@@ -231,6 +383,28 @@ class SmtpServerTest {
             out = socket.getOutputStream();
         }
 
+        /** Upgrade the connection to TLS (any certificate is trusted — the test server's is self-signed). */
+        void startTls() throws Exception {
+            SSLContext context = SSLContext.getInstance("TLS");
+            context.init(null, new TrustManager[]{new X509TrustManager() {
+                public void checkClientTrusted(X509Certificate[] chain, String authType) {
+                }
+
+                public void checkServerTrusted(X509Certificate[] chain, String authType) {
+                }
+
+                public X509Certificate[] getAcceptedIssuers() {
+                    return new X509Certificate[0];
+                }
+            }}, null);
+            SSLSocket ssl = (SSLSocket) context.getSocketFactory().createSocket(socket, "127.0.0.1", socket.getPort(), true);
+            ssl.setUseClientMode(true);
+            ssl.startHandshake();
+            socket = ssl;
+            in = new BufferedReader(new InputStreamReader(ssl.getInputStream(), StandardCharsets.UTF_8));
+            out = ssl.getOutputStream();
+        }
+
         void write(String text) throws Exception {
             out.write(text.getBytes(StandardCharsets.UTF_8));
             out.flush();

docker-compose.image.yml

@@ -0,0 +1,84 @@
+# Same stand as docker-compose.jambotron.yml, but from the ready image — nothing is built on the VM:
+# gitea.jambotron.com/jambotron_gang/reactive-mail-server (Drone builds it from master, see .drone.yml).
+# Pin a build: MAIL_IMAGE_TAG=<first 8 chars of the master commit>; default latest (pulled again on every deploy).
+# Test deploy on Jambotron (v0.2.3 75.3): pick this file in the deploy wizard.
+# Outside, only the web client + API (service "mail", port 8080) through Jambotron's Caddy — give it a domain.
+# SMTP (3025) stays inside the VM's docker network; nothing is sent outside (OUTBOUND_MODE=off).
+# Secrets are generated on the first start into the "secrets" volume — nothing to type in, nothing in git.
+# Mailboxes admin@<MAIL_DOMAINS> and trap@mail.test (catch-all): passwords in the "mail" log on the first start
+# (Jambotron: project → Services → mail → Logs) and in /app/data/initial-passwords.txt
+# of the "mail" container (docker exec <mail container> cat /app/data/initial-passwords.txt).
+name: reactive-mail
+
+services:
+  secrets-init:
+    image: alpine:3.20
+    restart: "no"
+    command:
+      - sh
+      - -c
+      - |
+        umask 077
+        for name in DB_PASSWORD JWT_SECRET; do
+          [ -s /secrets/$$name ] || head -c 48 /dev/urandom | base64 | tr -dc 'A-Za-z0-9' > /secrets/$$name
+        done
+        # postgres reads it as uid 70, the app as uid 10001 — readable inside these containers only
+        chmod 644 /secrets/DB_PASSWORD /secrets/JWT_SECRET
+    volumes:
+      - secrets:/secrets
+
+  db:
+    # Debian, not -alpine: on Jambotron staging VMs (Alpine 3.24, kernel 6.18) the Alpine build of postgres
+    # dies with "Bus error" even on --version; the Debian build works (2026-11-05)
+    image: postgres:17
+    restart: unless-stopped
+    depends_on:
+      secrets-init:
+        condition: service_completed_successfully
+    environment:
+      POSTGRES_DB: mailserver
+      POSTGRES_USER: mail
+      POSTGRES_PASSWORD_FILE: /run/mail-secrets/DB_PASSWORD
+    volumes:
+      - pgdata:/var/lib/postgresql/data
+      - secrets:/run/mail-secrets:ro
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U mail -d mailserver"]
+      interval: 10s
+      timeout: 5s
+      retries: 10
+    mem_limit: 256m
+
+  mail:
+    image: gitea.jambotron.com/jambotron_gang/reactive-mail-server:${MAIL_IMAGE_TAG:-latest}
+    pull_policy: always
+    restart: unless-stopped
+    depends_on:
+      db:
+        condition: service_healthy
+    expose:
+      - "8080"   # web client + API → domain in Jambotron
+      - "3025"   # SMTP, inside the network only
+      - "3143"   # IMAP (STARTTLS), inside the network only — open it in Jambotron as an internal TCP port
+    environment:
+      DB_HOST: db
+      MAILSERVER_SECRETS_DIR: /run/mail-secrets
+      MAIL_DOMAINS: ${MAIL_DOMAINS:-mail.test}
+      MAIL_HOSTNAME: ${MAIL_HOSTNAME:-mail.test}
+      DKIM_DOMAIN: ${MAIL_DOMAINS:-mail.test}
+      # mail trap: mail to any address without its own mailbox here (also gmail.com etc.) goes into this mailbox
+      MAIL_CATCH_ALL: ${MAIL_CATCH_ALL:-trap@mail.test}
+      MAIL_REGISTRATION: ${MAIL_REGISTRATION:-true}   # test stand: anyone can create a mailbox in MAIL_DOMAINS (nothing goes outside)
+      OUTBOUND_MODE: "off"
+      SMTP_AUTH_WITHOUT_TLS: "true"   # SMTP is not reachable from outside the VM
+      SPF_ENABLED: "false"
+      DMARC_ENABLED: "false"
+    volumes:
+      - data:/app/data
+      - secrets:/run/mail-secrets:ro
+    mem_limit: 512m
+
+volumes:
+  secrets:
+  pgdata:
+  data:

docker-compose.jambotron.yml

@@ -2,7 +2,8 @@
 # Outside, only the web client + API (service "mail", port 8080) through Jambotron's Caddy — give it a domain.
 # SMTP (3025) stays inside the VM's docker network; nothing is sent outside (OUTBOUND_MODE=off).
 # Secrets are generated on the first start into the "secrets" volume — nothing to type in, nothing in git.
-# Mailboxes admin@<MAIL_DOMAINS> and trap@mail.test (catch-all): passwords in /app/data/initial-passwords.txt
+# Mailboxes admin@<MAIL_DOMAINS> and trap@mail.test (catch-all): passwords in the "mail" log on the first start
+# (Jambotron: project → Services → mail → Logs) and in /app/data/initial-passwords.txt
 # of the "mail" container (docker exec <mail container> cat /app/data/initial-passwords.txt).
 name: reactive-mail
 
@@ -56,6 +57,7 @@ services:
     expose:
       - "8080"   # web client + API → domain in Jambotron
       - "3025"   # SMTP, inside the network only
+      - "3143"   # IMAP (STARTTLS), inside the network only — open it in Jambotron as an internal TCP port
     environment:
       DB_HOST: db
       MAILSERVER_SECRETS_DIR: /run/mail-secrets

docker-compose.public.yml

@@ -0,0 +1,156 @@
+# Real mail on the internet (v0.2.3 75.6): receives mail for MAIL_DOMAINS and sends it straight to the recipients'
+# MX servers (port 25), DKIM-signed. From the ready image, like docker-compose.image.yml.
+#
+# Needs a VM of its own with a public address (Jambotron 60.8: «Публичный адрес» of the VM, SMTP «да» — port 25
+# is closed by default) — the ports below are published on that address:
+#   25   SMTP: mail from other servers (STARTTLS) and from mail programs
+#   587  submission: mail programs (STARTTLS + login) — the same SMTP listener as 25
+#   465  SMTPS: mail programs, implicit TLS
+#   993  IMAPS: mail programs, implicit TLS
+#   80   only for Let's Encrypt (HTTP-01) — service "acme"
+# The web client + API (service "mail", port 8080) goes through Jambotron's Caddy under ANOTHER name
+# (webmail.<domain>): the name MAIL_HOSTNAME points at the VM's public address, not at Caddy.
+#
+# DNS before the first start (the certificate is issued over HTTP on MAIL_HOSTNAME):
+#   A    mail.<domain>             → public address of the VM
+#   PTR  public address            → mail.<domain>        (hoster's panel: Reverse DNS)
+#   MX   <domain>                  → 10 mail.<domain>
+#   TXT  <domain>                  → "v=spf1 ip4:<public address> -all"
+#   TXT  _dmarc.<domain>           → "v=DMARC1; p=none; rua=mailto:postmaster@<domain>"
+#   TXT  mail._domainkey.<domain>  → printed in the "mail" log on the first start (DKIM key, kept in the data volume)
+#
+# Mailbox admin@<domain>: its password is in the "mail" log on the first start and in /app/data/initial-passwords.txt.
+# Registration is closed: new mailboxes only by the admin. No catch-all.
+# Defaults are ours (mail.jambocheck.com / jambocheck.com) — Jambotron deploys without a .env; another domain:
+# MAIL_HOSTNAME, MAIL_DOMAINS, ACME_EMAIL in .env next to this file.
+name: reactive-mail-public
+
+services:
+  secrets-init:
+    image: alpine:3.20
+    restart: "no"
+    command:
+      - sh
+      - -c
+      - |
+        umask 077
+        for name in DB_PASSWORD JWT_SECRET; do
+          [ -s /secrets/$$name ] || head -c 48 /dev/urandom | base64 | tr -dc 'A-Za-z0-9' > /secrets/$$name
+        done
+        chmod 644 /secrets/DB_PASSWORD /secrets/JWT_SECRET
+    volumes:
+      - secrets:/secrets
+
+  # Let's Encrypt for MAIL_HOSTNAME: issued on the first start, renewed 30 days before the end (checked twice a day).
+  # The deploy hook copies the pair to /tls (readable by the "mail" user 10001); the server reads it again within
+  # a minute — no restart
+  acme:
+    image: goacme/lego:v5.5.2
+    restart: unless-stopped
+    ports:
+      - "80:80"
+    entrypoint:
+      - sh
+      - -c
+      - |
+        cat > /usr/local/bin/jb-deploy <<'EOF'
+        #!/bin/sh
+        set -e
+        cp "$$LEGO_HOOK_CERT_PATH" /tls/cert.pem.new
+        cp "$$LEGO_HOOK_CERT_KEY_PATH" /tls/key.pem.new
+        chown 10001 /tls/cert.pem.new /tls/key.pem.new
+        chmod 600 /tls/key.pem.new
+        chmod 644 /tls/cert.pem.new
+        mv /tls/key.pem.new /tls/key.pem
+        mv /tls/cert.pem.new /tls/cert.pem
+        echo "certificate for $$LEGO_HOOK_CERT_DOMAINS copied to /tls"
+        EOF
+        chmod 755 /usr/local/bin/jb-deploy
+        while true; do
+          /lego run --accept-tos --email "$$ACME_EMAIL" --domains "$$MAIL_HOSTNAME" --key-type EC256 \
+            --http --http.address :80 --path /var/lib/lego --renew-days 30 --no-random-sleep \
+            --deploy-hook /usr/local/bin/jb-deploy || echo "lego failed — next try in 1 hour"
+          [ -s /tls/cert.pem ] && sleep 43200 || sleep 3600
+        done
+    environment:
+      MAIL_HOSTNAME: ${MAIL_HOSTNAME:-mail.jambocheck.com}
+      ACME_EMAIL: ${ACME_EMAIL:-postmaster@jambocheck.com}
+      LEGO_LOG_FORMAT: text
+    volumes:
+      - lego:/var/lib/lego
+      - tls:/tls
+    healthcheck:
+      test: ["CMD-SHELL", "test -s /tls/cert.pem && test -s /tls/key.pem"]
+      interval: 15s
+      timeout: 5s
+      start_period: 10m
+      retries: 3
+    mem_limit: 128m
+
+  db:
+    image: postgres:17
+    restart: unless-stopped
+    depends_on:
+      secrets-init:
+        condition: service_completed_successfully
+    environment:
+      POSTGRES_DB: mailserver
+      POSTGRES_USER: mail
+      POSTGRES_PASSWORD_FILE: /run/mail-secrets/DB_PASSWORD
+    volumes:
+      - pgdata:/var/lib/postgresql/data
+      - secrets:/run/mail-secrets:ro
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U mail -d mailserver"]
+      interval: 10s
+      timeout: 5s
+      retries: 10
+    mem_limit: 256m
+
+  mail:
+    image: gitea.jambotron.com/jambotron_gang/reactive-mail-server:${MAIL_IMAGE_TAG:-latest}
+    pull_policy: always
+    restart: unless-stopped
+    depends_on:
+      db:
+        condition: service_healthy
+      acme:
+        condition: service_healthy   # waits for the first certificate
+    ports:
+      - "25:3025"
+      - "587:3025"
+      - "465:3465"
+      - "993:3993"
+    expose:
+      - "8080"   # web client + API → webmail.<domain> in Jambotron
+    environment:
+      DB_HOST: db
+      MAILSERVER_SECRETS_DIR: /run/mail-secrets
+      MAIL_DOMAINS: ${MAIL_DOMAINS:-jambocheck.com}
+      MAIL_HOSTNAME: ${MAIL_HOSTNAME:-mail.jambocheck.com}
+      MAIL_TLS_CERT: /tls/cert.pem
+      MAIL_TLS_KEY: /tls/key.pem
+      SMTPS_PORT: "3465"
+      IMAPS_PORT: "3993"
+      DKIM_DOMAIN: ${MAIL_DOMAINS:-jambocheck.com}
+      DKIM_SELECTOR: mail
+      DKIM_KEYS_DIR: /app/data/dkim-keys
+      MAIL_CATCH_ALL: ""
+      MAIL_REGISTRATION: "false"
+      OUTBOUND_MODE: mx
+      SMTP_AUTH_WITHOUT_TLS: "false"
+      IMAP_AUTH_WITHOUT_TLS: "false"
+      SPF_ENABLED: "true"
+      DMARC_ENABLED: "true"
+    volumes:
+      - data:/app/data
+      - secrets:/run/mail-secrets:ro
+      - tls:/tls:ro
+    mem_limit: 512m
+
+volumes:
+  secrets:
+  pgdata:
+  data:
+  lego:
+  tls: