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danil-smirnov / docker-postfix

Postfix Docker image with SMTP authentication, TLS and OpenDKIM support
MIT License
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docker-postfix

Run postfix with SMTP authentication (sasldb) in a Docker container.
TLS and OpenDKIM support is optional. Fail2ban can be enabled.

Installation

  1. Pull image

    docker pull danilsmirnov/postfix

Usage

  1. Create postfix container with smtp authentication

    docker run -p 25:25 \
    -e MAIL_DOMAIN=example.com -e SMTP_USER=user:pwd \
    --name postfix -d danilsmirnov/postfix
# Set multiple user credentials: -e SMTP_USER=user1:pwd1,user2:pwd2,...,userN:pwdN

  2. Set mail host defferent from mail domain

    docker run -p 25:25 \
    -e MAIL_DOMAIN=example.com -e MAIL_HOST=mail.example.com -e SMTP_USER=user:pwd \
    --name postfix -d danilsmirnov/postfix

  3. Enable OpenDKIM: save your domain key mail.private in /path/to/domainkeys

    docker run -p 25:25 \
    -e MAIL_DOMAIN=example.com -e MAIL_HOST=mail.example.com -e SMTP_USER=user:pwd \
    -v /path/to/domainkeys:/etc/opendkim/domainkeys \
    --name postfix -d danilsmirnov/postfix
# Set DKIM_SELECTOR variable if not okay with default "mail" selector

    To sign more domains add their key file(s) named $DKIM_SELECTOR._domainkey.$DOMAIN.private, e.g.:

    mail._domainkey.subdomain.example.com.private
mail._domainkey.*.example.com.private

    (Wildcard subdomain refers to its parent domain's DNS record.)

  4. Enable TLS(587): save your SSL certificates mail.example.com.key and mail.example.com.crt to /path/to/certs

    docker run -p 587:587 \
    -e MAIL_DOMAIN=example.com -e MAIL_HOST=mail.example.com -e SMTP_USER=user:pwd \
    -v /path/to/certs:/etc/postfix/certs \
    --name postfix -d danilsmirnov/postfix

  5. Enable Fail2ban with postfix-sasl jail to ban brute-force attackers

    docker run -p 25:25 \
    -e MAIL_DOMAIN=example.com -e MAIL_HOST=mail.example.com -e SMTP_USER=user:pwd \
    -e FAIL2BAN=enabled --cap-add NET_ADMIN \
    --name postfix -d danilsmirnov/postfix
# Note: NET_ADMIN capability must be granted to the container
# FAIL2BAN_BANTIME, FAIL2BAN_FINDTIME and FAIL2BAN_MAXRETRY could be set as well

  6. Add your custom configuration script /configure.sh

    docker run -p 25:25 \
    -e MAIL_DOMAIN=example.com -e MAIL_HOST=mail.example.com -e SMTP_USER=user:pwd \
    -v /path/to/script:/configure.sh \
    --name postfix -d danilsmirnov/postfix

    E.g., add an alias to forward mail to:

    postconf -e "virtual_alias_maps = hash:/etc/postfix/virtual"
echo "mailbox@${MAIL_DOMAIN} address@domain.com" > /etc/postfix/virtual
postmap /etc/postfix/virtual

Note

Reference

Credits