reactive-mail-server/backend/src/main/java/com/mailserver/config/MailServerConfig.java

package com.mailserver.config;

import com.mailserver.delivery.SmtpDeliveryClient;
import com.mailserver.smtp.MailRouter;
import com.mailserver.smtp.SmtpServer;
import com.mailserver.smtp.SmtpTls;
import io.netty.handler.ssl.SslContext;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableScheduling;

import java.nio.file.Path;
import java.time.Duration;
import java.util.Locale;

/** SMTP server, outbound delivery client and the queue scheduler. */
@Configuration
@EnableScheduling
public class MailServerConfig {

    /**
     * Certificate for SMTP TLS: mailserver.tls.cert-file + key-file (PEM), or a self-signed one in mailserver.tls.dir.
     * mailserver.tls.enabled=false — no TLS at all.
     */
    @Bean
    public SmtpTlsContext smtpTlsContext(@Value("${mailserver.tls.enabled:true}") boolean enabled,
                                         @Value("${mailserver.tls.cert-file:}") String certFile,
                                         @Value("${mailserver.tls.key-file:}") String keyFile,
                                         @Value("${mailserver.tls.dir:./tls}") String dir,
                                         @Value("${mailserver.smtp.hostname:localhost}") String hostname) throws Exception {
        return new SmtpTlsContext(enabled ? SmtpTls.serverContext(certFile, keyFile, Path.of(dir), hostname) : null);
    }

    public record SmtpTlsContext(SslContext context) {
    }

    @Bean(initMethod = "start", destroyMethod = "stop")
    @ConditionalOnProperty(name = "mailserver.smtp.enabled", havingValue = "true", matchIfMissing = true)
    public SmtpServer smtpServer(MailRouter router, SmtpTlsContext tls,
                                 @Value("${mailserver.smtp.host:0.0.0.0}") String host,
                                 @Value("${mailserver.smtp.port:3025}") int port,
                                 @Value("${mailserver.smtp.hostname:localhost}") String hostname,
                                 @Value("${mailserver.smtp.max-message-bytes:26214400}") long maxBytes,
                                 @Value("${mailserver.smtp.auth-without-tls:false}") boolean authWithoutTls,
                                 @Value("${mailserver.smtp.idle-timeout:5m}") Duration idleTimeout) {
        return new SmtpServer(new SmtpServer.Settings(host, port, hostname, maxBytes, authWithoutTls, idleTimeout,
                tls.context(), false), router);
    }

    /** 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 ${mailserver.tls.enabled:true}")
    public SmtpServer smtpsServer(MailRouter router, SmtpTlsContext tls,
                                  @Value("${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);
    }

    /**
     * mailserver.outbound.mode: off | mx | smarthost. For smarthost — host, port, username, password,
     * tls (starttls | ssl | none).
     */
    @Bean
    public SmtpDeliveryClient smtpDeliveryClient(@Value("${mailserver.outbound.mode:off}") String mode,
                                                 @Value("${mailserver.outbound.host:}") String host,
                                                 @Value("${mailserver.outbound.port:587}") int port,
                                                 @Value("${mailserver.outbound.username:}") String username,
                                                 @Value("${mailserver.outbound.password:}") String password,
                                                 @Value("${mailserver.outbound.tls:starttls}") String tls,
                                                 @Value("${mailserver.smtp.hostname:localhost}") String hostname,
                                                 @Value("${mailserver.outbound.timeout-ms:30000}") int timeoutMs) {
        SmtpDeliveryClient.Mode m = SmtpDeliveryClient.Mode.valueOf(mode.trim().toUpperCase(Locale.ROOT));
        if (m == SmtpDeliveryClient.Mode.SMARTHOST && host.isBlank()) {
            throw new IllegalStateException("mailserver.outbound.mode=smarthost needs mailserver.outbound.host");
        }
        return new SmtpDeliveryClient(new SmtpDeliveryClient.Settings(m, host, port, username, password,
                SmtpDeliveryClient.Tls.valueOf(tls.trim().toUpperCase(Locale.ROOT)), hostname, timeoutMs, 25));
    }
}