Ящики: минимальная длина пароля 8 (как при регистрации и смене пароля), было 10

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.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

@@ -2,7 +2,23 @@
 
 Почтовый сервер на **Spring Boot WebFlux + R2DBC (PostgreSQL) + Angular**: свой SMTP-сервер на Reactor Netty, веб-почта, очередь отправки, DKIM/SPF/DMARC.
 
-Назначение — наши личные цели (v0.2.3, раздел 75 чек-листа Jambotron): тестовый проект на Jambotron, ловушка почты для dev/staging. Для писем пользователям Jambotron (регистрация, сброс пароля) остаётся Resend.
+Назначение — наша настоящая почта **https://mail.jambocheck.com** (prod Jambotron, системная ВМ, адрес `103.109.235.154`) и тестовый проект на Jambotron.
+
+## Забыл пароль — где взять
+
+**Регистрации нет:** ящики создаёт администратор `admin@jambocheck.com` — веб-почта → Настройки → **MAILBOXES**.
+
+**Администратор:** `admin@jambocheck.com`, пароль `eK-6oj3TMtZgoXVxlvtCWFI6` (начальный, записан 2026-11-07 по решению владельца; сменили — обновить здесь).
+
+Пароли остальных ящиков (`staging@`, `no-reply@`, `monitor@`) — в репозитории Jambotron: `INFRASTRUCTURE/SECRETS.md`, раздел «Почта mail.jambocheck.com».
+
+| Ситуация | Что делать |
+| :--- | :--- |
+| Пароль `admin@` ещё не меняли | файл `/app/data/initial-passwords.txt` **внутри контейнера** `mail` на ВМ почты (в этом репозитории его нет; лежит в томе `data`, передеплой его не стирает). С компьютера: `ssh root@103.109.235.150`, затем `incus exec --project jambotron-prod incust-prod-react-mail-server -- docker exec jambotron-109cf3bb-mail-1 cat /app/data/initial-passwords.txt`. В логе `mail` строка `Mailbox created…` есть **только до первого передеплоя** |
+| Пароль `admin@` сменили и забыли | новый пароль прямо в базе почты, ящик и письма остаются — попросить α/Ω; команда — Jambotron, `INFRASTRUCTURE/test-stands.md`, раздел «Почта mail.jambocheck.com» |
+| Забыт пароль другого ящика (`staging@`, `no-reply@`, `monitor@`, свой) | войти под `admin@` → Настройки → MAILBOXES → ключик у ящика → новый пароль (показывается один раз) и вписать его туда, где ящик настроен |
+
+Всё о prod-почте (порты, DNS, кто через неё шлёт) — Jambotron, `INFRASTRUCTURE/test-stands.md`.
 
 ## Как устроено
 
@@ -13,7 +29,7 @@
 ```
 
 - **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.
+- **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`.
@@ -67,12 +83,14 @@ API: `GET /api/config` (без входа), `/api/me`, `/api/me/password`, `/api
 | `MAIL_DOMAINS` | наши домены, через запятую | `localhost` |
 | `MAIL_HOSTNAME` | имя сервера в SMTP | `localhost` |
 | `MAIL_ADMIN_EMAIL`, `MAIL_ADMIN_PASSWORD` | первый ящик на пустой базе; без пароля — случайный (в `MAIL_PASSWORDS_FILE` или один раз в логе) | `admin@<первый домен>` |
+| `MAIL_ADMINS` | кто управляет ящиками (Настройки → Mailboxes: создать, новый пароль, выключить), через запятую | первый ящик (`MAIL_ADMIN_EMAIL` или `admin@<первый домен>`) |
+| `HTTPS_PORT` | веб-клиент и API по HTTPS тем же сертификатом, что SMTP/IMAP (в `docker-compose.public.yml` — 8443 → 443: `https://mail.<домен>`); 0 — только HTTP на `server.port` | 0 |
 | `MAIL_PASSWORDS_FILE` | файл (права 600), куда дописываются случайные пароли созданных ящиков: первого и ловушки | — (в образе `/app/data/initial-passwords.txt`) |
 | `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; без них — самоподписанный | — |
+| `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` |
@@ -83,6 +101,22 @@ API: `GET /api/config` (без входа), `/api/me`, `/api/me/password`, `/api
 | `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
 
@@ -113,15 +147,61 @@ 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
 
-- [ ] Сертификат Let's Encrypt для настоящей почты (75.6): сейчас — свой файл или самоподписанный.
 - [ ] 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/src/main/java/com/mailserver/config/HttpsConfig.java

@@ -0,0 +1,81 @@
+package com.mailserver.config;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
+import org.springframework.context.SmartLifecycle;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.server.reactive.HttpHandler;
+import org.springframework.http.server.reactive.ReactorHttpHandlerAdapter;
+import reactor.netty.DisposableServer;
+import reactor.netty.http.server.HttpServer;
+
+import java.time.Duration;
+
+/**
+ * The web client and API over HTTPS on the mail host itself (mailserver.https.port, in public compose 8443 →
+ * published 443): https://mail.jambocheck.com opens the web mail, no second name through Jambotron's Caddy.
+ * Same certificate as SMTP/IMAP (Let's Encrypt from the acme service, reloaded when renewed). The plain HTTP port
+ * (8080) stays for a reverse proxy inside the network (staging: domain in Jambotron).
+ */
+@Configuration
+public class HttpsConfig {
+
+    @Bean
+    @ConditionalOnExpression("${mailserver.https.port:0} > 0 and ${mailserver.tls.enabled:true}")
+    public HttpsServer httpsServer(HttpHandler handler, MailServerConfig.SmtpTlsContext tls,
+                                   @Value("${mailserver.smtp.host:0.0.0.0}") String host,
+                                   @Value("${mailserver.https.port}") int port) {
+        return new HttpsServer(handler, tls, host, port);
+    }
+
+    public static class HttpsServer implements SmartLifecycle {
+
+        private static final Logger log = LoggerFactory.getLogger(HttpsServer.class);
+
+        private final HttpHandler handler;
+        private final MailServerConfig.SmtpTlsContext tls;
+        private final String host;
+        private final int port;
+        private volatile DisposableServer server;
+
+        HttpsServer(HttpHandler handler, MailServerConfig.SmtpTlsContext tls, String host, int port) {
+            this.handler = handler;
+            this.tls = tls;
+            this.host = host;
+            this.port = port;
+        }
+
+        @Override
+        public void start() {
+            server = HttpServer.create()
+                    .host(host)
+                    .port(port)
+                    .secure(spec -> spec.sslContext(tls.context()))
+                    // HSTS: Spring Security adds it for HTTPS requests by itself
+                    .handle(new ReactorHttpHandlerAdapter(handler))
+                    .bindNow(Duration.ofSeconds(30));
+            log.info("HTTPS (web client + API) listening on {}:{}", host, server.port());
+        }
+
+        @Override
+        public void stop() {
+            DisposableServer current = server;
+            if (current != null) {
+                current.disposeNow(Duration.ofSeconds(10));
+                server = null;
+            }
+        }
+
+        @Override
+        public boolean isRunning() {
+            return server != null;
+        }
+
+        public int port() {
+            return server == null ? -1 : server.port();
+        }
+    }
+}

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

@@ -1,5 +1,6 @@
 package com.mailserver.config;
 
+import com.mailserver.security.LoginGuard;
 import com.mailserver.imap.DbImapStore;
 import com.mailserver.imap.ImapServer;
 import com.mailserver.imap.ImapStore;
@@ -32,7 +33,7 @@ public class ImapConfig {
 
     @Bean(initMethod = "start", destroyMethod = "stop")
     @ConditionalOnProperty(name = "mailserver.imap.enabled", havingValue = "true", matchIfMissing = true)
-    public ImapServer imapServer(ImapStore store, MailServerConfig.SmtpTlsContext tls,
+    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("${mailserver.smtp.hostname:localhost}") String hostname,
@@ -41,12 +42,12 @@ public class ImapConfig {
                                  @Value("${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);
+                (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 ${mailserver.tls.enabled:true}")
-    public ImapServer imapsServer(ImapStore store, MailServerConfig.SmtpTlsContext tls,
+    public ImapServer imapsServer(ImapStore store, MailServerConfig.SmtpTlsContext tls, LoginGuard guard,
                                   @Value("${mailserver.imap.host:0.0.0.0}") String host,
                                   @Value("${mailserver.imaps.port}") int port,
                                   @Value("${mailserver.smtp.hostname:localhost}") String hostname,
@@ -54,6 +55,6 @@ public class ImapConfig {
                                   @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);
+                (int) maxLiteral.toBytes(), idleTimeout, idlePoll), store, guard);
     }
 }

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/MailAdmins.java

@@ -0,0 +1,36 @@
+package com.mailserver.config;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Component;
+
+import java.util.Arrays;
+import java.util.Locale;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+/**
+ * Who manages mailboxes (Settings → Mailboxes): {@code mailserver.admins} (comma separated), by default the first
+ * mailbox — {@code mailserver.admin.email}, or admin@<first domain>. No role in the database: the list lives in
+ * the configuration, so a stolen mailbox can not make itself an administrator.
+ */
+@Component
+public class MailAdmins {
+
+    private final Set<String> admins;
+
+    public MailAdmins(@Value("${mailserver.admins:}") String admins,
+                      @Value("${mailserver.admin.email:}") String firstMailbox,
+                      MailDomains domains) {
+        String list = !admins.isBlank() ? admins
+                : !firstMailbox.isBlank() ? firstMailbox
+                : "admin@" + domains.domains().iterator().next();
+        this.admins = Arrays.stream(list.split(","))
+                .map(a -> a.trim().toLowerCase(Locale.ROOT))
+                .filter(a -> !a.isEmpty())
+                .collect(Collectors.toUnmodifiableSet());
+    }
+
+    public boolean isAdmin(String email) {
+        return email != null && admins.contains(email.toLowerCase(Locale.ROOT));
+    }
+}

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

@@ -1,5 +1,6 @@
 package com.mailserver.config;
 
+import com.mailserver.security.LoginGuard;
 import com.mailserver.delivery.SmtpDeliveryClient;
 import com.mailserver.smtp.MailRouter;
 import com.mailserver.smtp.SmtpServer;
@@ -39,7 +40,7 @@ public class MailServerConfig {
 
     @Bean(initMethod = "start", destroyMethod = "stop")
     @ConditionalOnProperty(name = "mailserver.smtp.enabled", havingValue = "true", matchIfMissing = true)
-    public SmtpServer smtpServer(MailRouter router, SmtpTlsContext tls,
+    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("${mailserver.smtp.hostname:localhost}") String hostname,
@@ -47,20 +48,20 @@ public class MailServerConfig {
                                  @Value("${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,
-                tls.context(), false), router);
+                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 ${mailserver.tls.enabled:true}")
-    public SmtpServer smtpsServer(MailRouter router, SmtpTlsContext tls,
+    public SmtpServer smtpsServer(MailRouter router, SmtpTlsContext tls, LoginGuard guard,
                                   @Value("${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);
+                tls.context(), true), router, guard);
     }
 
     /**

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

@@ -1,5 +1,6 @@
 package com.mailserver.controller;
 
+import com.mailserver.config.MailAdmins;
 import com.mailserver.config.MailDomains;
 import com.mailserver.domain.User;
 import com.mailserver.dto.LoginRequest;
@@ -10,11 +11,16 @@ 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 +31,8 @@ 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 +42,10 @@ 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 +55,14 @@ public class AuthenticationController {
     private final JwtUtils jwtUtils;
     private final MailDomains domains;
     private final boolean registrationEnabled;
+    private final LoginGuard guard;
+    private final MailAdmins admins;
 
     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, MailAdmins admins) {
+        this.guard = guard;
+        this.admins = admins;
         this.userService = userService;
         this.mailService = mailService;
         this.jwtUtils = jwtUtils;
@@ -60,23 +77,34 @@ public class AuthenticationController {
     }
 
     @PostMapping("/login")
-    public Mono<ResponseEntity<?>> login(@Valid @RequestBody Mono<LoginRequest> requestMono) {
+    public Mono<ResponseEntity<?>> login(@Valid @RequestBody Mono<LoginRequest> requestMono, ServerHttpRequest http) {
-        return requestMono.flatMap(request ->
+        String ip = clientIp(http);
-            userService.findByEmail(request.getEmail().trim().toLowerCase(Locale.ROOT))
+        return requestMono.flatMap(request -> {
-                .switchIfEmpty(Mono.error(new IllegalArgumentException("Invalid credentials")))
+            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). */
@@ -116,16 +144,46 @@ 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,
-                        user.getQuotaBytes() == null ? 0 : user.getQuotaBytes(), user.getCreatedAt()));
+                        user.getQuotaBytes() == null ? 0 : user.getQuotaBytes(), user.getCreatedAt(),
+                        admins.isAdmin(user.getEmail())));
     }
 
     private Mono<User> user(Mono<Authentication> auth) {

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

@@ -0,0 +1,184 @@
+package com.mailserver.controller;
+
+import com.mailserver.config.MailAdmins;
+import com.mailserver.config.MailDomains;
+import com.mailserver.domain.User;
+import com.mailserver.dto.LoginResponse;
+import com.mailserver.service.MailService;
+import com.mailserver.service.UserService;
+import com.mailserver.util.JwtUtils;
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.Size;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.http.HttpStatus;
+import org.springframework.security.core.Authentication;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.PutMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.ResponseStatus;
+import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.server.ResponseStatusException;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import java.security.SecureRandom;
+import java.time.Instant;
+import java.util.Base64;
+import java.util.Comparator;
+import java.util.Locale;
+import java.util.regex.Pattern;
+
+/**
+ * Mailboxes of this server for its administrators ({@link MailAdmins}): list, create (no-reply@, monitor@,
+ * support@ — registration stays closed), new password, switch off. A generated password is returned once, in the
+ * answer — it is not logged.
+ */
+@RestController
+@RequestMapping("/api/admin/mailboxes")
+public class MailboxAdminController {
+
+    private static final Logger log = LoggerFactory.getLogger(MailboxAdminController.class);
+    private static final Pattern LOCAL_PART = Pattern.compile("[a-z0-9](?:[a-z0-9._+-]{0,62}[a-z0-9])?");
+    private static final int MIN_PASSWORD = 8;
+
+    public record MailboxView(Long id, String email, String displayName, boolean active, boolean admin,
+                              long usedBytes, long quotaBytes, Instant createdAt) {
+    }
+
+    /** @param password empty — the server generates one and returns it once */
+    public record CreateRequest(@NotBlank @Size(max = 254) String email, @Size(max = 100) String displayName,
+                                @Size(max = 200) String password) {
+    }
+
+    public record PasswordRequest(@Size(max = 200) String password) {
+    }
+
+    public record ActiveRequest(boolean active) {
+    }
+
+    /** @param password the generated password, or null when the administrator chose it */
+    public record Created(MailboxView mailbox, String password) {
+    }
+
+    private final UserService users;
+    private final MailService mail;
+    private final MailDomains domains;
+    private final MailAdmins admins;
+    private final JwtUtils jwt;
+
+    public MailboxAdminController(UserService users, MailService mail, MailDomains domains, MailAdmins admins, JwtUtils jwt) {
+        this.jwt = jwt;
+        this.users = users;
+        this.mail = mail;
+        this.domains = domains;
+        this.admins = admins;
+    }
+
+    @GetMapping
+    public Flux<MailboxView> list(Mono<Authentication> auth) {
+        return admin(auth).thenMany(users.all())
+                .concatMap(this::view)
+                .sort(Comparator.comparing(MailboxView::email));
+    }
+
+    @PostMapping
+    @ResponseStatus(HttpStatus.CREATED)
+    public Mono<Created> create(Mono<Authentication> auth, @RequestBody Mono<CreateRequest> body) {
+        return admin(auth).then(body).flatMap(request -> {
+            String email = request.email() == null ? "" : request.email().trim().toLowerCase(Locale.ROOT);
+            int at = email.lastIndexOf('@');
+            if (at <= 0 || !LOCAL_PART.matcher(email.substring(0, at)).matches()) {
+                return Mono.error(bad("Not a mailbox address: " + email));
+            }
+            if (!domains.isLocal(email)) {
+                return Mono.error(bad("Mailboxes can be created only in " + String.join(", ", domains.domains().stream().sorted().toList())));
+            }
+            String chosen = request.password() == null ? "" : request.password();
+            if (!chosen.isEmpty() && chosen.length() < MIN_PASSWORD) {
+                return Mono.error(bad("Password: at least " + MIN_PASSWORD + " characters, or leave it empty to generate one"));
+            }
+            String password = chosen.isEmpty() ? randomPassword() : chosen;
+            return users.register(email, password, request.displayName())
+                    .onErrorMap(IllegalArgumentException.class, e -> new ResponseStatusException(HttpStatus.CONFLICT, "This mailbox already exists"))
+                    .doOnNext(user -> log.info("Mailbox created by administrator: {}", email))
+                    .flatMap(this::view)
+                    .map(view -> new Created(view, chosen.isEmpty() ? password : null));
+        });
+    }
+
+    /** New password: the given one, or a generated one returned once. */
+    @PostMapping("/{id}/password")
+    public Mono<Created> password(Mono<Authentication> auth, @PathVariable Long id, @RequestBody Mono<PasswordRequest> body) {
+        return admin(auth).then(body.defaultIfEmpty(new PasswordRequest(null))).flatMap(request -> {
+            String chosen = request.password() == null ? "" : request.password();
+            if (!chosen.isEmpty() && chosen.length() < MIN_PASSWORD) {
+                return Mono.error(bad("Password: at least " + MIN_PASSWORD + " characters, or leave it empty to generate one"));
+            }
+            String password = chosen.isEmpty() ? randomPassword() : chosen;
+            return mailbox(id)
+                    .flatMap(user -> users.setPassword(user, password))
+                    .doOnNext(user -> log.info("Password of {} set by administrator", user.getEmail()))
+                    .flatMap(this::view)
+                    .map(view -> new Created(view, chosen.isEmpty() ? password : null));
+        });
+    }
+
+    /**
+     * Administrator opens a mailbox without its password (Settings → MAILBOXES → Open): a session of that mailbox.
+     * Every opening is logged — who opened which mailbox.
+     */
+    @PostMapping("/{id}/open")
+    public Mono<LoginResponse> open(Mono<Authentication> auth, @PathVariable Long id) {
+        return admin(auth).flatMap(me -> mailbox(id).map(user -> {
+            log.warn("Administrator {} opened mailbox {}", me, user.getEmail());
+            LoginResponse response = new LoginResponse();
+            response.setToken(jwt.generateToken(user.getEmail()));
+            response.setEmail(user.getEmail());
+            return response;
+        }));
+    }
+
+    /** Switched off: no login (web, SMTP, IMAP); mail to it is still received. */
+    @PutMapping("/{id}/active")
+    public Mono<MailboxView> active(Mono<Authentication> auth, @PathVariable Long id, @RequestBody Mono<ActiveRequest> body) {
+        return admin(auth).flatMap(me -> body.flatMap(request -> mailbox(id).flatMap(user -> {
+            if (!request.active() && user.getEmail().equalsIgnoreCase(me)) {
+                return Mono.error(bad("You can not switch off your own mailbox"));
+            }
+            log.info("Mailbox {} {} by administrator", user.getEmail(), request.active() ? "switched on" : "switched off");
+            return users.setActive(user, request.active());
+        }))).flatMap(this::view);
+    }
+
+    private Mono<String> admin(Mono<Authentication> auth) {
+        return auth.switchIfEmpty(Mono.error(new ResponseStatusException(HttpStatus.UNAUTHORIZED)))
+                .map(Authentication::getName)
+                .filter(admins::isAdmin)
+                .switchIfEmpty(Mono.error(new ResponseStatusException(HttpStatus.FORBIDDEN, "Only for mail administrators")));
+    }
+
+    private Mono<User> mailbox(Long id) {
+        return users.byId(id).switchIfEmpty(Mono.error(new ResponseStatusException(HttpStatus.NOT_FOUND, "Mailbox not found")));
+    }
+
+    private Mono<MailboxView> view(User user) {
+        return mail.usedBytes(user.getId()).defaultIfEmpty(0L)
+                .map(used -> new MailboxView(user.getId(), user.getEmail(), user.getDisplayName(), user.isActive(),
+                        admins.isAdmin(user.getEmail()), used, user.getQuotaBytes() == null ? 0 : user.getQuotaBytes(),
+                        user.getCreatedAt()));
+    }
+
+    private static ResponseStatusException bad(String message) {
+        return new ResponseStatusException(HttpStatus.BAD_REQUEST, message);
+    }
+
+    static String randomPassword() {
+        byte[] bytes = new byte[18];
+        new SecureRandom().nextBytes(bytes);
+        return Base64.getUrlEncoder().withoutPadding().encodeToString(bytes);
+    }
+}

backend/src/main/java/com/mailserver/dto/ProfileResponse.java

@@ -2,5 +2,7 @@ package com.mailserver.dto;
 
 import java.time.Instant;
 
-public record ProfileResponse(String email, String displayName, long usedBytes, long quotaBytes, Instant createdAt) {
+/** @param admin may manage mailboxes ({@link com.mailserver.config.MailAdmins}) */
+public record ProfileResponse(String email, String displayName, long usedBytes, long quotaBytes, Instant createdAt,
+                              boolean admin) {
 }

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

@@ -1,5 +1,6 @@
 package com.mailserver.imap;
 
+import com.mailserver.security.LoginGuard;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
 import io.netty.channel.ChannelHandlerContext;
@@ -67,11 +68,17 @@ public class ImapServer {
 
     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() {
@@ -98,7 +105,7 @@ public class ImapServer {
                     });
                     ImapSession session = new ImapSession(
                             new ImapSession.Settings(settings.hostname(), settings.tls() != null, settings.authWithoutTls()),
-                            store, remoteIp[0], settings.implicitTls());
+                            store, guard, remoteIp[0], settings.implicitTls());
                     @SuppressWarnings("unchecked")
                     Sinks.Empty<Void>[] idleDone = new Sinks.Empty[1];
 
@@ -135,7 +142,9 @@ public class ImapServer {
                                 log.debug("IMAP {}: connection closed: {}", session.remoteIp, e.toString());
                                 return Mono.just(ImapSession.line("* BYE " + e.getMessage()));
                             })
-                            .takeUntil(response -> session.closing);
+                            // 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
@@ -164,6 +173,10 @@ public class ImapServer {
         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);
     }

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

@@ -1,5 +1,6 @@
 package com.mailserver.imap;
 
+import com.mailserver.security.LoginGuard;
 import com.mailserver.service.LocalDelivery;
 import jakarta.mail.Session;
 import jakarta.mail.internet.MimeMessage;
@@ -9,6 +10,7 @@ import org.slf4j.LoggerFactory;
 
 import java.io.ByteArrayInputStream;
 import java.nio.charset.StandardCharsets;
+import java.time.Duration;
 import java.time.Instant;
 import java.time.LocalDate;
 import java.time.ZoneOffset;
@@ -39,6 +41,8 @@ final class ImapSession {
     private static final Logger log = LoggerFactory.getLogger(ImapSession.class);
 
     private static final int MAX_BAD_COMMANDS = 30;
+    /** Wrong passwords in one connection before it is closed. */
+    private static final int MAX_AUTH_FAILURES = 3;
     private static final int SOURCE_CACHE = 16;
     private static final DateTimeFormatter INTERNAL_DATE =
             DateTimeFormatter.ofPattern("dd-MMM-yyyy HH:mm:ss Z", Locale.ENGLISH);
@@ -53,6 +57,7 @@ final class ImapSession {
 
     private final Settings settings;
     private final ImapStore store;
+    private final LoginGuard guard;
     final String remoteIp;
 
     boolean tls;
@@ -78,8 +83,13 @@ final class ImapSession {
     volatile String idleTag;
 
     ImapSession(Settings settings, ImapStore store, String remoteIp, boolean tls) {
+        this(settings, store, LoginGuard.disabled(), remoteIp, tls);
+    }
+
+    ImapSession(Settings settings, ImapStore store, LoginGuard guard, String remoteIp, boolean tls) {
         this.settings = settings;
         this.store = store;
+        this.guard = guard;
         this.remoteIp = remoteIp;
         this.tls = tls;
     }
@@ -254,7 +264,7 @@ final class ImapSession {
             out.add(line(tag + " NO [PRIVACYREQUIRED] Use STARTTLS first"));
             return;
         }
-        loggedIn(tag, store.authenticate(user, password), user, out);
+        checkPassword(tag, user, password, out);
     }
 
     private void authenticate(String tag, ImapReader in, List<byte[]> out) {
@@ -292,13 +302,44 @@ final class ImapSession {
             bad(tag, "Bad PLAIN response", out);
             return;
         }
-        loggedIn(tag, store.authenticate(fields[1], fields[2]), fields[1], out);
+        checkPassword(tag, fields[1], fields[2], out);
+    }
+
+    /** Through the login guard: a blocked IP/mailbox gets no answer about the password and the connection closes. */
+    private void checkPassword(String tag, String user, String password, List<byte[]> out) {
+        Duration wait = guard.retryAfter(remoteIp, user);
+        if (!wait.isZero()) {
+            log.warn("IMAP {}: login as {} refused, blocked for {}", remoteIp, user, LoginGuard.human(wait));
+            out.add(line("* BYE Too many failed logins, try again in " + LoginGuard.human(wait)));
+            out.add(line(tag + " NO [UNAVAILABLE] Too many failed logins"));
+            closing = true;
+            return;
+        }
+        ImapStore.Account result = store.authenticate(user, password);
+        if (result == null) {
+            guard.failure(remoteIp, user);
+            pause(guard.failureDelay());
+        } else {
+            guard.success(remoteIp, user);
+        }
+        loggedIn(tag, result, user, out);
+    }
+
+    private static void pause(Duration delay) {
+        if (delay.isZero()) {
+            return;
+        }
+        try {
+            Thread.sleep(delay.toMillis());
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+        }
     }
 
     private void loggedIn(String tag, ImapStore.Account result, String user, List<byte[]> out) {
         if (result == null) {
             log.warn("IMAP {}: authentication failed for {}", remoteIp, user);
-            if (++badCommands > 5) {
+            if (++badCommands >= MAX_AUTH_FAILURES) {
                 out.add(line("* BYE Too many failed logins"));
                 closing = true;
             }

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/UserService.java

@@ -74,6 +74,25 @@ public class UserService {
         return userRepository.save(user).then();
     }
 
+    public Flux<User> all() {
+        return userRepository.findAll();
+    }
+
+    public Mono<User> byId(Long id) {
+        return userRepository.findById(id);
+    }
+
+    /** Administrator sets a new password (Settings → Mailboxes): no current password needed. */
+    public Mono<User> setPassword(User user, String newPassword) {
+        user.setPassword(passwordEncoder.encode(newPassword));
+        return userRepository.save(user);
+    }
+
+    public Mono<User> setActive(User user, boolean active) {
+        user.setActive(active);
+        return userRepository.save(user);
+    }
+
     public Mono<User> updateDisplayName(User user, String displayName) {
         user.setDisplayName(displayName.trim());
         return userRepository.save(user);

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

@@ -1,5 +1,6 @@
 package com.mailserver.smtp;
 
+import com.mailserver.security.LoginGuard;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufUtil;
 import io.netty.channel.ChannelHandlerContext;
@@ -54,6 +55,8 @@ 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");
 
@@ -84,11 +87,17 @@ public class SmtpServer {
 
     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() {
@@ -183,6 +192,7 @@ public class SmtpServer {
         final ByteArrayOutputStream data = new ByteArrayOutputStream();
         boolean dataTooBig;
         int badCommands;
+        int authFailures;
         volatile boolean closing;
 
         Session(String remoteIp, boolean tls) {
@@ -356,16 +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);
                     });
         }
 

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

@@ -22,6 +22,7 @@ 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;
@@ -30,7 +31,8 @@ import java.util.Date;
 /**
  * Certificate for SMTP TLS (STARTTLS and implicit TLS):
  * <ul>
- *   <li>{@code cert} and {@code key} given (PEM: certificate chain and PKCS#8 key, e.g. from Let's Encrypt) — used as is;</li>
+ *   <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>
@@ -41,6 +43,7 @@ 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() {
     }
@@ -67,7 +70,8 @@ public final class SmtpTls {
                 log.info("SMTP TLS: self-signed certificate {}", cert);
             }
         }
-        return SslContextBuilder.forServer(cert.toFile(), key.toFile())
+        // 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();
     }

backend/src/main/resources/application.properties

@@ -27,6 +27,8 @@ mailserver.catch-all=${MAIL_CATCH_ALL:}
 mailserver.registration.enabled=${MAIL_REGISTRATION:false}
 mailserver.admin.email=${MAIL_ADMIN_EMAIL:}
 mailserver.admin.password=${MAIL_ADMIN_PASSWORD:}
+# Who manages mailboxes (Settings → Mailboxes), comma separated; empty — the first mailbox (admin.email or admin@<first domain>)
+mailserver.admins=${MAIL_ADMINS:}
 # Generated passwords of created mailboxes (first admin, catch-all) are appended here (mode 600); empty — printed to the log once
 mailserver.passwords-file=${MAIL_PASSWORDS_FILE:}
 mailserver.cors.origins=${MAIL_CORS_ORIGINS:}
@@ -47,6 +49,8 @@ mailserver.tls.enabled=${MAIL_TLS:true}
 mailserver.tls.cert-file=${MAIL_TLS_CERT:}
 mailserver.tls.key-file=${MAIL_TLS_KEY:}
 mailserver.tls.dir=${MAIL_TLS_DIR:./tls}
+# Web client + API over HTTPS with the same certificate (public compose: 8443 → 443); 0 — only plain HTTP (server.port)
+mailserver.https.port=${HTTPS_PORT:0}
 mailserver.smtps.port=${SMTPS_PORT:0}
 
 # Outbound: off | mx (straight to recipients' MX, port 25) | smarthost (via a provider, e.g. Resend)
@@ -83,3 +87,15 @@ 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/test/java/com/mailserver/config/HttpsConfigTest.java

@@ -0,0 +1,45 @@
+package com.mailserver.config;
+
+import com.mailserver.smtp.SmtpTls;
+import io.netty.handler.ssl.SslContextBuilder;
+import io.netty.handler.ssl.util.InsecureTrustManagerFactory;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import org.springframework.core.io.buffer.DefaultDataBufferFactory;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.server.reactive.HttpHandler;
+import reactor.core.publisher.Mono;
+import reactor.netty.http.client.HttpClient;
+
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Path;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/** https://mail.jambocheck.com: the web client over HTTPS with the mail certificate. */
+class HttpsConfigTest {
+
+    @Test
+    void servesTheWebAppOverTls(@TempDir Path dir) throws Exception {
+        MailServerConfig.SmtpTlsContext tls = new MailServerConfig.SmtpTlsContext(SmtpTls.serverContext("", "", dir, "localhost"));
+        HttpHandler handler = (request, response) -> {
+            response.setStatusCode(HttpStatus.OK);
+            return response.writeWith(Mono.just(DefaultDataBufferFactory.sharedInstance
+                    .wrap(("hello " + request.getURI().getScheme()).getBytes(StandardCharsets.UTF_8))));
+        };
+        io.netty.handler.ssl.SslContext trustAll = SslContextBuilder.forClient().trustManager(InsecureTrustManagerFactory.INSTANCE).build();
+        HttpsConfig.HttpsServer server = new HttpsConfig.HttpsServer(handler, tls, "127.0.0.1", 0);
+        server.start();
+        try {
+            assertThat(server.isRunning()).isTrue();
+            String body = HttpClient.create()
+                    .secure(spec -> spec.sslContext(trustAll))
+                    .get().uri("https://127.0.0.1:" + server.port() + "/")
+                    .responseContent().aggregate().asString().block();
+            assertThat(body).isEqualTo("hello https");
+        } finally {
+            server.stop();
+        }
+        assertThat(server.isRunning()).isFalse();
+    }
+}

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, mock(com.mailserver.config.MailAdmins.class));
+
+    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/controller/MailboxAdminControllerTest.java

@@ -0,0 +1,143 @@
+package com.mailserver.controller;
+
+import com.mailserver.config.MailAdmins;
+import com.mailserver.config.MailDomains;
+import com.mailserver.domain.User;
+import com.mailserver.service.MailService;
+import com.mailserver.service.UserService;
+import org.junit.jupiter.api.Test;
+import org.springframework.http.HttpStatus;
+import org.springframework.security.authentication.UsernamePasswordAuthenticationToken;
+import org.springframework.security.core.Authentication;
+import org.springframework.web.server.ResponseStatusException;
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyLong;
+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;
+
+/** Settings → Mailboxes: only administrators; mailboxes only in our domains; a generated password comes back once. */
+class MailboxAdminControllerTest {
+
+    private final UserService users = mock(UserService.class);
+    private final MailService mail = mock(MailService.class);
+    private final MailDomains domains = new MailDomains("jambocheck.com", "");
+    private final MailAdmins admins = new MailAdmins("", "", domains);
+    private final com.mailserver.util.JwtUtils jwt = mock(com.mailserver.util.JwtUtils.class);
+    private final MailboxAdminController controller = new MailboxAdminController(users, mail, domains, admins, jwt);
+
+    private final User admin = user(1L, "admin@jambocheck.com");
+    private final User alice = user(2L, "alice@jambocheck.com");
+
+    MailboxAdminControllerTest() {
+        when(mail.usedBytes(anyLong())).thenReturn(Mono.just(0L));
+        when(users.all()).thenReturn(Flux.just(alice, admin));
+        when(users.byId(1L)).thenReturn(Mono.just(admin));
+        when(users.byId(2L)).thenReturn(Mono.just(alice));
+        when(users.byId(99L)).thenReturn(Mono.empty());
+        when(users.register(anyString(), anyString(), any())).thenAnswer(i -> Mono.just(user(3L, i.getArgument(0))));
+        when(users.setPassword(any(), anyString())).thenAnswer(i -> Mono.just((User) i.getArgument(0)));
+        when(users.setActive(any(), any(Boolean.class))).thenAnswer(i -> {
+            User u = i.getArgument(0);
+            u.setActive(i.getArgument(1));
+            return Mono.just(u);
+        });
+    }
+
+    @Test
+    void administratorIsTheFirstMailboxByDefault() {
+        assertThat(admins.isAdmin("ADMIN@jambocheck.com")).isTrue();
+        assertThat(admins.isAdmin("alice@jambocheck.com")).isFalse();
+        assertThat(new MailAdmins("ops@jambocheck.com, root@jambocheck.com", "admin@jambocheck.com", domains).isAdmin("admin@jambocheck.com")).isFalse();
+    }
+
+    @Test
+    void listsMailboxesSortedForAnAdministratorOnly() {
+        List<MailboxAdminController.MailboxView> list = controller.list(as("admin@jambocheck.com")).collectList().block();
+        assertThat(list).extracting(MailboxAdminController.MailboxView::email).containsExactly("admin@jambocheck.com", "alice@jambocheck.com");
+        assertThat(list.get(0).admin()).isTrue();
+
+        assertThat(status(() -> controller.list(as("alice@jambocheck.com")).collectList().block())).isEqualTo(HttpStatus.FORBIDDEN);
+    }
+
+    @Test
+    void createsReservedNamesWithAGeneratedPasswordShownOnce() {
+        var created = controller.create(as("admin@jambocheck.com"),
+                Mono.just(new MailboxAdminController.CreateRequest(" No-Reply@JamboCheck.com ", "Jambotron", ""))).block();
+
+        assertThat(created.mailbox().email()).isEqualTo("no-reply@jambocheck.com");
+        assertThat(created.password()).hasSizeGreaterThanOrEqualTo(20);
+        verify(users).register(eq("no-reply@jambocheck.com"), eq(created.password()), eq("Jambotron"));
+
+        var chosen = controller.create(as("admin@jambocheck.com"),
+                Mono.just(new MailboxAdminController.CreateRequest("monitor@jambocheck.com", null, "long-enough-1"))).block();
+        assertThat(chosen.password()).isNull();
+    }
+
+    @Test
+    void refusesOtherDomainsBadAddressesShortPasswordsAndNonAdmins() {
+        assertThat(status(() -> create("admin@jambocheck.com", "x@gmail.com", ""))).isEqualTo(HttpStatus.BAD_REQUEST);
+        assertThat(status(() -> create("admin@jambocheck.com", "bad address@jambocheck.com", ""))).isEqualTo(HttpStatus.BAD_REQUEST);
+        assertThat(status(() -> create("admin@jambocheck.com", "x@jambocheck.com", "short"))).isEqualTo(HttpStatus.BAD_REQUEST);
+        assertThat(status(() -> create("alice@jambocheck.com", "x@jambocheck.com", ""))).isEqualTo(HttpStatus.FORBIDDEN);
+        verify(users, never()).register(anyString(), anyString(), any());
+
+        when(users.register(eq("alice@jambocheck.com"), anyString(), any())).thenReturn(Mono.error(new IllegalArgumentException("exists")));
+        assertThat(status(() -> create("admin@jambocheck.com", "alice@jambocheck.com", ""))).isEqualTo(HttpStatus.CONFLICT);
+    }
+
+    @Test
+    void newPasswordAndSwitchOffButNotYourself() {
+        var reset = controller.password(as("admin@jambocheck.com"), 2L, Mono.just(new MailboxAdminController.PasswordRequest(null))).block();
+        assertThat(reset.password()).isNotBlank();
+        verify(users).setPassword(alice, reset.password());
+
+        assertThat(controller.active(as("admin@jambocheck.com"), 2L, Mono.just(new MailboxAdminController.ActiveRequest(false))).block().active()).isFalse();
+        assertThat(status(() -> controller.active(as("admin@jambocheck.com"), 1L, Mono.just(new MailboxAdminController.ActiveRequest(false))).block()))
+                .isEqualTo(HttpStatus.BAD_REQUEST);
+    }
+
+    @Test
+    void administratorOpensAnyMailboxOthersCanNot() {
+        when(jwt.generateToken("alice@jambocheck.com")).thenReturn("alice-token");
+
+        var session = controller.open(as("admin@jambocheck.com"), 2L).block();
+        assertThat(session.getEmail()).isEqualTo("alice@jambocheck.com");
+        assertThat(session.getToken()).isEqualTo("alice-token");
+
+        assertThat(status(() -> controller.open(as("alice@jambocheck.com"), 1L).block())).isEqualTo(HttpStatus.FORBIDDEN);
+        assertThat(status(() -> controller.open(as("admin@jambocheck.com"), 99L).block())).isEqualTo(HttpStatus.NOT_FOUND);
+    }
+
+    private MailboxAdminController.Created create(String me, String email, String password) {
+        return controller.create(as(me), Mono.just(new MailboxAdminController.CreateRequest(email, null, password))).block();
+    }
+
+    private static Mono<Authentication> as(String email) {
+        return Mono.just(new UsernamePasswordAuthenticationToken(email, null, List.of()));
+    }
+
+    private static HttpStatus status(Runnable call) {
+        Throwable error = org.assertj.core.api.Assertions.catchThrowable(call::run);
+        assertThat(error).isInstanceOf(ResponseStatusException.class);
+        return HttpStatus.valueOf(((ResponseStatusException) error).getStatusCode().value());
+    }
+
+    private static User user(Long id, String email) {
+        User user = new User();
+        user.setId(id);
+        user.setEmail(email);
+        user.setPassword("hash");
+        return user;
+    }
+}

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

@@ -14,6 +14,7 @@ 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;
@@ -184,6 +185,33 @@ class ImapServerTest {
         }
     }
 
+    @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())) {

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

@@ -5,6 +5,7 @@ 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;
@@ -158,6 +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())) {

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.public.yml

@@ -0,0 +1,159 @@
+# 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"
+#   443  web client + API over HTTPS, same Let's Encrypt certificate (acme): https://mail.jambocheck.com
+# The web client + API can also go through Jambotron's Caddy (plain port 8080) 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"
+      - "443:8443"   # web client + API over HTTPS: https://mail.jambocheck.com
+    expose:
+      - "8080"   # plain HTTP, for a reverse proxy inside the network (not needed on the public address)
+    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"
+      HTTPS_PORT: "8443"
+      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:

frontend/src/app/core/api.service.ts

@@ -1,7 +1,7 @@
 import { Injectable, inject } from '@angular/core';
 import { HttpClient } from '@angular/common/http';
 import { Observable } from 'rxjs';
-import { Attachment, BlacklistEntry, Contact, Draft, Folder, Message, Profile, ServerConfig } from './models';
+import { Attachment, BlacklistEntry, Contact, Draft, Folder, Mailbox, MailboxCreated, Message, Profile, ServerConfig } from './models';
 
 /** The mail server REST API (same origin, /api). */
 @Injectable({ providedIn: 'root' })
@@ -17,6 +17,21 @@ export class ApiService {
     return this.http.put('/api/me/password', { currentPassword, newPassword });
   }
 
+  // mailboxes — administrators only
+  mailboxes(): Observable<Mailbox[]> { return this.http.get<Mailbox[]>('/api/admin/mailboxes'); }
+  createMailbox(email: string, displayName: string, password: string): Observable<MailboxCreated> {
+    return this.http.post<MailboxCreated>('/api/admin/mailboxes', { email, displayName, password });
+  }
+  newMailboxPassword(id: number): Observable<MailboxCreated> {
+    return this.http.post<MailboxCreated>(`/api/admin/mailboxes/${id}/password`, {});
+  }
+  openMailbox(id: number): Observable<{ token: string; email: string }> {
+    return this.http.post<{ token: string; email: string }>(`/api/admin/mailboxes/${id}/open`, {});
+  }
+  setMailboxActive(id: number, active: boolean): Observable<Mailbox> {
+    return this.http.put<Mailbox>(`/api/admin/mailboxes/${id}/active`, { active });
+  }
+
   // folders
   folders(): Observable<Folder[]> { return this.http.get<Folder[]>('/api/folders'); }
   createFolder(name: string): Observable<Folder> { return this.http.post<Folder>('/api/folders', { name }); }

frontend/src/app/core/auth.service.ts

@@ -12,6 +12,8 @@ export class AuthService {
   private router = inject(Router);
 
   readonly email = signal<string | null>(read('email'));
+  /** Administrator who opened this mailbox (Settings → MAILBOXES → Open), or null */
+  readonly openedBy = signal<string | null>(read('adminEmail'));
   readonly loggedIn = computed(() => this.email() !== null && read('token') !== null);
 
   login(email: string, password: string): Observable<TokenResponse> {
@@ -24,6 +26,32 @@ export class AuthService {
 
   token(): string | null { return read('token'); }
 
+  /** Administrator opens another mailbox: its session, the admin session kept to come back. */
+  openAs(response: TokenResponse): void {
+    const adminToken = read('token');
+    const adminEmail = read('email');
+    try {
+      if (adminToken && adminEmail && !read('adminToken')) {
+        localStorage.setItem('adminToken', adminToken);
+        localStorage.setItem('adminEmail', adminEmail);
+      }
+    } catch { /* storage blocked */ }
+    this.store(response);
+    this.openedBy.set(read('adminEmail'));
+  }
+
+  /** Back to the administrator's own mailbox. */
+  backToAdmin(): void {
+    const token = read('adminToken');
+    const email = read('adminEmail');
+    try {
+      localStorage.removeItem('adminToken');
+      localStorage.removeItem('adminEmail');
+    } catch { /* storage blocked */ }
+    this.openedBy.set(null);
+    if (token && email) { this.store({ token, email }); } else { this.clear(); }
+  }
+
   logout(): void {
     this.clear();
     this.router.navigate(['/login']);
@@ -33,8 +61,11 @@ export class AuthService {
     try {
       localStorage.removeItem('token');
       localStorage.removeItem('email');
+      localStorage.removeItem('adminToken');
+      localStorage.removeItem('adminEmail');
     } catch { /* storage blocked */ }
     this.email.set(null);
+    this.openedBy.set(null);
   }
 
   private store(response: TokenResponse): void {

frontend/src/app/core/models.ts

@@ -53,6 +53,25 @@ export interface Profile {
   usedBytes: number;
   quotaBytes: number;
   createdAt: string;
+  admin?: boolean;        // may manage mailboxes (Settings → Mailboxes)
+}
+
+/** MailboxAdminController.MailboxView */
+export interface Mailbox {
+  id: number;
+  email: string;
+  displayName: string;
+  active: boolean;
+  admin: boolean;
+  usedBytes: number;
+  quotaBytes: number;
+  createdAt: string;
+}
+
+/** password — generated by the server, shown once; null when the administrator chose it */
+export interface MailboxCreated {
+  mailbox: Mailbox;
+  password: string | null;
 }
 
 export interface ServerConfig {

frontend/src/app/pages/auth/register.page.ts

@@ -49,13 +49,21 @@ const NAME = /^[a-z0-9]([a-z0-9._-]{0,62}[a-z0-9])?$/;
           </div>
           <div>
             <label class="synth-label" for="password">Password (8+ characters)</label>
-            <input id="password" name="password" type="password" class="synth-input" [ngModel]="password()"
+            <div class="relative"><input id="password" name="password" [type]="show() ? 'text' : 'password'" class="synth-input pr-10" [ngModel]="password()"
                    (ngModelChange)="password.set($event)" required minlength="8" autocomplete="new-password">
+            <button type="button" class="absolute right-2 top-1/2 -translate-y-1/2 text-slate-400 hover:text-cyan-300"
+                    [attr.aria-label]="show() ? 'Hide password' : 'Show password'" (click)="show.set(!show())">
+              <mat-icon>{{ show() ? 'visibility_off' : 'visibility' }}</mat-icon>
+            </button></div>
           </div>
           <div>
             <label class="synth-label" for="password2">Password again</label>
-            <input id="password2" name="password2" type="password" class="synth-input" [ngModel]="password2()"
+            <div class="relative"><input id="password2" name="password2" [type]="show() ? 'text' : 'password'" class="synth-input pr-10" [ngModel]="password2()"
                    (ngModelChange)="password2.set($event)" required autocomplete="new-password">
+            <button type="button" class="absolute right-2 top-1/2 -translate-y-1/2 text-slate-400 hover:text-cyan-300"
+                    [attr.aria-label]="show() ? 'Hide password' : 'Show password'" (click)="show.set(!show())">
+              <mat-icon>{{ show() ? 'visibility_off' : 'visibility' }}</mat-icon>
+            </button></div>
           </div>
           @if (error()) {
             <p class="text-sm text-pink-400 font-rajdhani flex items-center gap-2" role="alert">
@@ -79,6 +87,7 @@ export class RegisterPage {
 
   readonly loaded = signal(false);
   readonly enabled = signal(false);
+  readonly show = signal(false);
   readonly domains = signal<string[]>([]);
   readonly domain = signal('');
   readonly local = signal('');

frontend/src/app/pages/folder/folder.page.ts

@@ -67,7 +67,7 @@ import { ToastService } from '../../ui/toast.service';
           </div>
         </ng-template>
         <ng-template jtGridCell="subject" let-row>
-          <a [routerLink]="link(row)" class="block max-w-[560px] group">
+          <a [routerLink]="link(row)" class="block max-w-[480px] group">
             <span class="truncate block group-hover:text-cyan-300" [class.font-bold]="!row.read" [class.text-white]="!row.read">
               @if (!row.read) { <span class="inline-block w-2 h-2 rounded-full bg-pink-500 mr-1.5 align-middle shadow-[0_0_8px_#ff007f]" aria-label="Unread"></span> }
               {{ row.subject || '(no subject)' }}

frontend/src/app/pages/settings/mailboxes.section.ts

@@ -0,0 +1,164 @@
+import { ChangeDetectionStrategy, Component, computed, inject, signal } from '@angular/core';
+import { FormsModule } from '@angular/forms';
+import { MatIconModule } from '@angular/material/icon';
+import { ApiService } from '../../core/api.service';
+import { MailStateService } from '../../core/mail-state.service';
+import { Mailbox, errorText, formatBytes } from '../../core/models';
+import { ToastService } from '../../ui/toast.service';
+import { AuthService } from '../../core/auth.service';
+
+/** Settings → Mailboxes (administrators): create no-reply@, monitor@, support@ …, new password, switch off. */
+@Component({
+  selector: 'app-mailboxes-section',
+  imports: [FormsModule, MatIconModule],
+  changeDetection: ChangeDetectionStrategy.OnPush,
+  // ячейка сетки настроек — сам элемент компонента: на две колонки
+  host: { class: 'block xl:col-span-2' },
+  template: `
+    <section class="glass-panel static p-5 md:p-6" aria-labelledby="mailboxes-title">
+      <h2 id="mailboxes-title" class="text-lg font-orbitron font-bold text-cyan-300 flex items-center gap-2 mb-4 border-b border-cyan-500/20 pb-2">
+        <mat-icon class="text-pink-500">group</mat-icon> MAILBOXES
+      </h2>
+
+      <form (ngSubmit)="create()" class="grid grid-cols-1 md:grid-cols-[1fr_1fr_1fr_auto] gap-3 items-end mb-4">
+        <div><label class="synth-label" for="mb-email">Address</label>
+          <div class="flex items-stretch gap-2">
+            <input id="mb-email" name="email" class="synth-input" [ngModel]="local()" (ngModelChange)="local.set($event.toLowerCase().trim())"
+                   placeholder="no-reply" autocomplete="off" required>
+            <span class="flex items-center text-cyan-300 font-mono">&#64;</span>
+            @if (domains().length > 1) {
+              <select name="domain" class="synth-input !w-auto" [ngModel]="domain()" (ngModelChange)="domain.set($event)" aria-label="Domain">
+                @for (d of domains(); track d) { <option [value]="d">{{ d }}</option> }
+              </select>
+            } @else {
+              <span class="flex items-center px-3 rounded-[10px] bg-slate-900/70 border border-cyan-500/30 font-mono text-sm text-slate-200 whitespace-nowrap">{{ domain() }}</span>
+            }
+          </div></div>
+        <div><label class="synth-label" for="mb-name">Name</label>
+          <input id="mb-name" name="name" class="synth-input" [(ngModel)]="name" maxlength="100" autocomplete="off"></div>
+        <div><label class="synth-label" for="mb-password">Password (empty — generate)</label>
+          <div class="relative"><input id="mb-password" name="password" [type]="showPw() ? 'text' : 'password'" class="synth-input pr-10" [(ngModel)]="password" autocomplete="new-password">
+            <button type="button" class="absolute right-2 top-1/2 -translate-y-1/2 text-slate-400 hover:text-cyan-300"
+                    [attr.aria-label]="showPw() ? 'Hide password' : 'Show password'" (click)="showPw.set(!showPw())">
+              <mat-icon>{{ showPw() ? 'visibility_off' : 'visibility' }}</mat-icon>
+            </button></div></div>
+        <button type="submit" class="cyber-btn px-4 py-2 rounded-lg text-xs font-bold" [disabled]="busy()"><mat-icon>add</mat-icon> CREATE</button>
+      </form>
+      @if (error()) { <p class="text-sm text-pink-400 mb-3" role="alert">{{ error() }}</p> }
+
+      @if (secret(); as s) {
+        <div class="p-3 mb-4 rounded-lg border border-pink-500/40 bg-slate-900/60" role="status">
+          <div class="text-xs text-slate-400 mb-1">Password of <span class="font-mono text-cyan-300">{{ s.email }}</span> — shown once, copy it now</div>
+          <div class="flex items-center gap-2">
+            <code class="font-mono text-pink-300 break-all select-all">{{ s.password }}</code>
+            <button type="button" class="ghost-btn !py-1" (click)="copy(s.password)" aria-label="Copy password"><mat-icon>content_copy</mat-icon></button>
+            <button type="button" class="ghost-btn !py-1" (click)="secret.set(null)" aria-label="Hide password"><mat-icon>close</mat-icon></button>
+          </div>
+        </div>
+      }
+
+      <ul class="divide-y divide-cyan-500/10">
+        @for (m of mailboxes(); track m.id) {
+          <li class="flex flex-wrap items-center gap-x-4 gap-y-1 py-2">
+            <span class="font-mono text-sm" [class.text-cyan-300]="m.active" [class.text-slate-500]="!m.active" [class.line-through]="!m.active">{{ m.email }}</span>
+            <span class="text-sm text-slate-400">{{ m.displayName }}</span>
+            @if (m.admin) { <span class="text-[10px] font-mono px-1.5 rounded border border-pink-500/40 text-pink-300">ADMIN</span> }
+            <span class="text-xs font-mono text-slate-500 ml-auto">{{ size(m.usedBytes) }}</span>
+            @if (m.email !== me()) {
+              <button type="button" class="ghost-btn !py-1" (click)="open(m)" [attr.aria-label]="'Open ' + m.email" title="Open mailbox">
+                <mat-icon>mark_email_read</mat-icon> OPEN</button>
+            }
+            <button type="button" class="ghost-btn !py-1" (click)="newPassword(m)" [attr.aria-label]="'New password for ' + m.email"><mat-icon>key</mat-icon></button>
+            @if (m.email !== me()) {
+              <button type="button" class="ghost-btn !py-1" (click)="toggle(m)"
+                      [attr.aria-label]="(m.active ? 'Switch off ' : 'Switch on ') + m.email">
+                <mat-icon>{{ m.active ? 'toggle_on' : 'toggle_off' }}</mat-icon></button>
+            }
+          </li>
+        }
+      </ul>
+    </section>
+  `
+})
+export class MailboxesSection {
+  private api = inject(ApiService);
+  private state = inject(MailStateService);
+  private toasts = inject(ToastService);
+  private auth = inject(AuthService);
+
+  readonly mailboxes = signal<Mailbox[]>([]);
+  readonly secret = signal<{ email: string; password: string } | null>(null);
+  readonly error = signal('');
+  readonly busy = signal(false);
+  readonly me = computed(() => this.state.profile()?.email ?? '');
+  readonly showPw = signal(false);
+  readonly local = signal('');
+  // Домены сервера (/api/config); пока не пришли — домен своего ящика
+  readonly domains = signal<string[]>([]);
+  readonly domain = signal('');
+  name = '';
+  password = '';
+
+  constructor() {
+    this.domain.set(this.me().split('@')[1] ?? '');
+    this.api.config().subscribe({
+      next: c => { this.domains.set(c.domains); if (!c.domains.includes(this.domain())) { this.domain.set(c.domains[0] ?? ''); } },
+      error: () => {}
+    });
+    this.load();
+  }
+
+  size(bytes: number): string {
+    return formatBytes(bytes);
+  }
+
+  load(): void {
+    this.api.mailboxes().subscribe({ next: list => this.mailboxes.set(list), error: e => this.error.set(errorText(e)) });
+  }
+
+  create(): void {
+    const local = this.local().replace(/@.*$/, '');
+    if (!local) { this.error.set('Enter an address'); return; }
+    const email = local + '@' + this.domain();
+    this.error.set('');
+    this.busy.set(true);
+    this.api.createMailbox(email, this.name.trim(), this.password).subscribe({
+      next: created => {
+        this.busy.set(false);
+        this.local.set('');
+        this.name = this.password = '';
+        if (created.password) { this.secret.set({ email: created.mailbox.email, password: created.password }); }
+        this.toasts.ok('Mailbox ' + created.mailbox.email + ' created');
+        this.load();
+      },
+      error: e => { this.busy.set(false); this.error.set(errorText(e)); }
+    });
+  }
+
+  newPassword(m: Mailbox): void {
+    if (!confirm('New password for ' + m.email + '? The old one stops working at once.')) return;
+    this.api.newMailboxPassword(m.id).subscribe({
+      next: created => created.password && this.secret.set({ email: m.email, password: created.password }),
+      error: e => this.toasts.error(errorText(e))
+    });
+  }
+
+  /** Administrator reads this mailbox: its session; the banner on top leads back. Full reload — fresh folders. */
+  open(m: Mailbox): void {
+    this.api.openMailbox(m.id).subscribe({
+      next: session => { this.auth.openAs(session); location.assign('/'); },
+      error: e => this.toasts.error(errorText(e))
+    });
+  }
+
+  toggle(m: Mailbox): void {
+    this.api.setMailboxActive(m.id, !m.active).subscribe({
+      next: () => this.load(),
+      error: e => this.toasts.error(errorText(e))
+    });
+  }
+
+  copy(text: string): void {
+    navigator.clipboard?.writeText(text).then(() => this.toasts.ok('Copied'), () => this.toasts.error('Copy it by hand'));
+  }
+}

frontend/src/app/pages/settings/settings.page.ts

@@ -7,11 +7,12 @@ import { MailStateService } from '../../core/mail-state.service';
 import { errorText, formatBytes } from '../../core/models';
 import { THEMES, ThemeService } from '../../ui/theme.service';
 import { ToastService } from '../../ui/toast.service';
+import { MailboxesSection } from './mailboxes.section';
 
 /** Profile name, password, storage, look. */
 @Component({
   selector: 'app-settings',
-  imports: [DatePipe, FormsModule, MatIconModule],
+  imports: [DatePipe, FormsModule, MatIconModule, MailboxesSection],
   changeDetection: ChangeDetectionStrategy.OnPush,
   template: `
     <div class="grid grid-cols-1 xl:grid-cols-2 gap-5">
@@ -41,11 +42,23 @@ import { ToastService } from '../../ui/toast.service';
         <form (ngSubmit)="changePassword()" class="space-y-3">
           <input type="email" name="username" class="sr-only" [value]="state.profile()?.email ?? ''" autocomplete="username" tabindex="-1" aria-hidden="true">
           <div><label class="synth-label" for="pw-current">Current password</label>
-            <input id="pw-current" name="current" type="password" class="synth-input" [(ngModel)]="current" autocomplete="current-password"></div>
+            <div class="relative"><input id="pw-current" name="current" [type]="showPw() ? 'text' : 'password'" class="synth-input pr-10" [(ngModel)]="current" autocomplete="current-password">
+            <button type="button" class="absolute right-2 top-1/2 -translate-y-1/2 text-slate-400 hover:text-cyan-300"
+                    [attr.aria-label]="showPw() ? 'Hide password' : 'Show password'" (click)="showPw.set(!showPw())">
+              <mat-icon>{{ showPw() ? 'visibility_off' : 'visibility' }}</mat-icon>
+            </button></div></div>
           <div><label class="synth-label" for="pw-new">New password (8+ characters)</label>
-            <input id="pw-new" name="next" type="password" class="synth-input" [(ngModel)]="next" autocomplete="new-password"></div>
+            <div class="relative"><input id="pw-new" name="next" [type]="showPw() ? 'text' : 'password'" class="synth-input pr-10" [(ngModel)]="next" autocomplete="new-password">
+            <button type="button" class="absolute right-2 top-1/2 -translate-y-1/2 text-slate-400 hover:text-cyan-300"
+                    [attr.aria-label]="showPw() ? 'Hide password' : 'Show password'" (click)="showPw.set(!showPw())">
+              <mat-icon>{{ showPw() ? 'visibility_off' : 'visibility' }}</mat-icon>
+            </button></div></div>
           <div><label class="synth-label" for="pw-again">New password again</label>
-            <input id="pw-again" name="again" type="password" class="synth-input" [(ngModel)]="again" autocomplete="new-password"></div>
+            <div class="relative"><input id="pw-again" name="again" [type]="showPw() ? 'text' : 'password'" class="synth-input pr-10" [(ngModel)]="again" autocomplete="new-password">
+            <button type="button" class="absolute right-2 top-1/2 -translate-y-1/2 text-slate-400 hover:text-cyan-300"
+                    [attr.aria-label]="showPw() ? 'Hide password' : 'Show password'" (click)="showPw.set(!showPw())">
+              <mat-icon>{{ showPw() ? 'visibility_off' : 'visibility' }}</mat-icon>
+            </button></div></div>
           @if (passwordError()) { <p class="text-sm text-pink-400" role="alert">{{ passwordError() }}</p> }
           <button type="submit" class="cyber-btn px-4 py-2 rounded-lg text-xs font-bold"><mat-icon>lock_reset</mat-icon> CHANGE PASSWORD</button>
         </form>
@@ -97,6 +110,10 @@ import { ToastService } from '../../ui/toast.service';
           </div>
         </div>
       </section>
+
+      @if (state.profile()?.admin) {
+        <app-mailboxes-section />
+      }
     </div>
   `
 })
@@ -112,6 +129,7 @@ export class SettingsPage {
   next = '';
   again = '';
   readonly passwordError = signal('');
+  readonly showPw = signal(false);
 
   readonly used = computed(() => formatBytes(this.state.profile()?.usedBytes));
   readonly quota = computed(() => formatBytes(this.state.profile()?.quotaBytes));

frontend/src/app/pages/shell/shell.component.ts

@@ -69,8 +69,17 @@ import { ToastService } from '../../ui/toast.service';
         </div>
       </header>
 
+      @if (auth.openedBy(); as admin) {
+        <div class="bg-pink-600/90 text-white text-sm font-rajdhani px-4 py-2 flex flex-wrap items-center justify-center gap-3" role="status">
+          <mat-icon class="!text-base">visibility</mat-icon>
+          <span>You are in mailbox <b class="font-mono">{{ auth.email() }}</b> as administrator</span>
+          <button type="button" class="ghost-btn !py-1 !border-white !text-white" (click)="backToAdmin()">
+            <mat-icon>arrow_back</mat-icon> Back to {{ admin }}</button>
+        </div>
+      }
+
       <div class="flex-grow max-w-[1500px] w-full mx-auto p-3 md:p-5 grid grid-cols-1 lg:grid-cols-[260px_1fr] gap-5">
-        <nav class="glass-panel static p-4 h-fit lg:sticky lg:top-24 lg:block" [class.hidden]="!menuOpen()"
+        <nav class="glass-panel static p-4 md:pt-6 h-fit lg:sticky lg:top-20 lg:block" [class.hidden]="!menuOpen()"
              aria-label="Mail folders">
           <a routerLink="/compose" class="cyber-btn w-full py-2.5 rounded-xl font-bold text-xs mb-4" (click)="menuOpen.set(false)">
             <mat-icon>edit</mat-icon> COMPOSE
@@ -247,6 +256,11 @@ export class ShellComponent {
     }
   }
 
+  backToAdmin(): void {
+    this.auth.backToAdmin();
+    location.assign('/settings');
+  }
+
   logout(): void {
     this.state.reset();
     this.auth.logout();