feat(mail): 支持 SMTP Submission 由 API 接管

- 新增 `465/587` 提交服务与 TLS 配置，支持 StartTLS 和隐式 TLS。
- 提交时校验认证邮箱、权限和 `From` 一致性，先写入 `Sent` 再转发到后端 SMTP。
- 增加 `Message-ID` 去重与失败回滚，避免重复保存发送副本。
- 调整部署与文档，移除 Postfix 的 submission 监听，改由 LanQin API 对外提供提交端口。

deploy/postfix/Dockerfile

@@ -11,5 +11,5 @@ COPY master.cf /etc/postfix/master.cf
 COPY sqlite-*.cf /etc/postfix/
 COPY entrypoint.sh /entrypoint.sh
 RUN chmod +x /entrypoint.sh
-EXPOSE 25 465 587
+EXPOSE 25
 CMD ["/entrypoint.sh"]

deploy/postfix/main.cf

@@ -14,13 +14,11 @@ virtual_transport = lmtp:inet:dovecot:24
 virtual_mailbox_base = /var/mail/vhosts
 
 smtpd_banner = $myhostname ESMTP LanQin Email
-smtpd_relay_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
-smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
+smtpd_relay_restrictions = permit_mynetworks, reject_unauth_destination
+smtpd_recipient_restrictions = permit_mynetworks, reject_unauth_destination
 
-# Submission auth via Dovecot.
-smtpd_sasl_type = dovecot
-smtpd_sasl_path = inet:dovecot:12345
-smtpd_sasl_auth_enable = yes
+# 465/587 提交由 LanQin API 处理；Postfix 25 只负责入站和内部 relay。
+smtpd_sasl_auth_enable = no
 smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
 smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
 smtpd_tls_security_level = may

deploy/postfix/master.cf

@@ -1,14 +1,4 @@
 smtp      inet  n       -       n       -       -       smtpd
-submission inet n       -       n       -       -       smtpd
-  -o syslog_name=postfix/submission
-  -o smtpd_tls_security_level=may
-  -o smtpd_sasl_auth_enable=yes
-  -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
-smtps     inet  n       -       n       -       -       smtpd
-  -o syslog_name=postfix/smtps
-  -o smtpd_tls_wrappermode=yes
-  -o smtpd_sasl_auth_enable=yes
-  -o smtpd_relay_restrictions=permit_sasl_authenticated,reject
 pickup    unix  n       -       n       60      1       pickup
 cleanup   unix  n       -       n       -       0       cleanup
 qmgr      unix  n       -       n       300     1       qmgr

deploy/postfix/sqlite-sender-bcc.cf

@@ -1,2 +0,0 @@
-dbpath = /data/lanqin.db
-query = SELECT local_part || '+Sent@' || substr(address, instr(address, '@') + 1) FROM mailboxes WHERE lower(address)=lower('%s') AND status='active'