メールサーバも普通にたてるより、Dockerで作った方が良いかも

https://github.com/docker-mailserver/docker-mailserver

今回は下記でSSLを用意しておく想定
10 Docker Let's Encrypt

cd /app/
git clone https://github.com/docker-mailserver/docker-mailserver.git

cd /app/docker-mailserver/

volumesにSSL証明書を読み込むように書きを追加してあります。

1. /var/lib/docker/volumes/app_certs/_data:/etc/letsencrypt/live

services:
  mailserver:
    image: ghcr.io/docker-mailserver/docker-mailserver:latest
    container_name: mailserver
    # Provide the FQDN of your mail server here (Your DNS MX record should point to this value)
    hostname: mail.hogehoge.com
    env_file: mailserver.env
    # More information about the mail-server ports:
    # https://docker-mailserver.github.io/docker-mailserver/latest/config/security/understanding-the-ports/
    # To avoid conflicts with yaml base-60 float, DO NOT remove the quotation marks.
    ports:
      - "25:25"    # SMTP  (explicit TLS => STARTTLS)
      - "143:143"  # IMAP4 (explicit TLS => STARTTLS)
      - "465:465"  # ESMTP (implicit TLS)
      - "587:587"  # ESMTP (explicit TLS => STARTTLS)
      - "993:993"  # IMAP4 (implicit TLS)
    volumes:
      - ./docker-data/dms/mail-data/:/var/mail/
      - ./docker-data/dms/mail-state/:/var/mail-state/
      - ./docker-data/dms/mail-logs/:/var/log/mail/
      - ./docker-data/dms/config/:/tmp/docker-mailserver/
      - /etc/localtime:/etc/localtime:ro
      - /var/lib/docker/volumes/app_certs/_data:/etc/letsencrypt/live
    restart: always
    stop_grace_period: 1m
    # Uncomment if using `ENABLE_FAIL2BAN=1`:
    cap_add:
      - NET_ADMIN
    healthcheck:
      test: "ss --listening --tcp | grep -P 'LISTEN.+:smtp' || exit 1"
      timeout: 3s
      retries: 0

# diff mailserver.env mailserver.env.org 
45c45
< POSTMASTER_ADDRESS=hoge@hogehoge.com
---
> POSTMASTER_ADDRESS=
91c91
< SPOOF_PROTECTION=1
---
> SPOOF_PROTECTION=
179c179
< ENABLE_DNSBL=1
---
> ENABLE_DNSBL=0
185c185
< ENABLE_FAIL2BAN=1
---
> ENABLE_FAIL2BAN=0
212c212
< SSL_TYPE=letsencrypt
---
> SSL_TYPE=
348c348
< ENABLE_SPAMASSASSIN=1
---
> ENABLE_SPAMASSASSIN=0
460c460
< ENABLE_POSTGREY=1
---
> ENABLE_POSTGREY=0

# docker-compose up -d

通常だとProcmail利用じゃないので、Procmailで配送するよう変更する場合imageを新たに作ります。

# Mail directory
virtual_transport = lmtp:unix:/var/run/dovecot/lmtp
virtual_mailbox_domains = /etc/postfix/vhost
virtual_mailbox_maps = texthash:/etc/postfix/vmailbox
virtual_alias_maps = texthash:/etc/postfix/virtual

↓

# Mail directory
virtual_transport = procmail
virtual_mailbox_domains = /etc/postfix/vhost
virtual_mailbox_maps = texthash:/etc/postfix/vmailbox
virtual_alias_maps = texthash:/etc/postfix/virtual
virtual_uid_maps = static:5000
virtual_gid_maps = static:5000

procmail  unix  -       n       n       -       -       pipe
  flags=R user=docker argv=/usr/bin/procmail -t -m USER=${user} DOMAIN=${nexthop} /tmp/docker-mailserver/procmailrc

procmailだけ追加インストール

RUN <<EOF
  rm -rf /usr/share/locale/*
  rm -rf /usr/share/man/*
  rm -rf /usr/share/doc/*
  update-locale
  apt update
  apt install -y procmail
EOF

DOCKER_BUILDKIT=1だけ入れて、build

DOCKER_BUILDKIT=1 docker image build -t mailserver2 .