docker-postfix

Postfix in a container with optional SMTP authentication (sasldb), DKIM support, TLS support.

Installation

Pull from docker hub

docker pull kingsquare/postfix

Build local image from repo

docker build -t kingsquare/postfix https://github.com/kingsquare/docker-postfix.git

Usage

1. Create postfix container with smtp authentication

   docker run \
       -p 25:25 \
       -p 587:587 \
       -e maildomain=mail.example.com \
       -e smtp_user=user:pwd \
       --name postfix \
       -d kingsquare/postfix
   
   # Set multiple user credentials: -e smtp_user=user1:pwd1,user2:pwd2,...,userN:pwdN

2. Create postfix container with smtp authentication

   docker run \
       -p 25:25 \
       -p 587:587 \
       -e maildomain=mail.example.com \
       -e smtp_user=/etc/postfix/smtp_user \
       --name postfix \
       -d kingsquare/postfix
   
   # Set multiple user credentials: -e smtp_user=user1:pwd1,user2:pwd2,...,userN:pwdN
   
   # Set multiple user credentials from file: -v /some/file:/etc/postfix/smtp_users
   

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

   docker run \
       -p 25:25 \
       -p 587:587 \
       -e maildomain=mail.example.com \
       -e smtp_user=user:pwd \
       -e dkimselector=mail \
       -v /path/to/domainkeys:/etc/opendkim/domainkeys \
       --name postfix \
       -d kingsquare/postfix

4. Enable OpenDKIM: override all config with custom directory

   docker run \
       -p 25:25 \
       -p 587:587 \
       -e maildomain=mail.example.com \
       -e smtp_user=user:pwd \
       -e dkimselector=mail \
       -v /path/to/etc/opendkim:/etc/opendkim \
       --name postfix \
       -d kingsquare/postfix

5. Enable TLS: add your SSL certificates .key and .crt files to /path/to/certs. If you have a combined crt+key file then make sure it's extension is .crt

   docker run \
       -p 25:25 \
       -p 587:587 \
       -e maildomain=mail.example.com \
       -e smtp_user=user:pwd \
       -v /path/to/certs:/etc/postfix/certs \
       --name postfix \
       -d kingsquare/postfix

6. Optional Postfix configuration passed using environment variables:

   • inet_protocols

     this allows postfix to limit the outgoing internet protocols to the given param (ipv4, ipv6, all (=default))

   • message_size_limit

     To in-/decrease the message size limit, set this to the required amount in bytes (default: 10240000 = 10MB)

To use this i.e. -e message_size_limit=51200000 to increase the limit to 50MB

Notes

• Login credential should be set to (username@mail.example.com, password) in SMTP Client
• You can assign the port of MTA on the host machine to one other than 25 (postfix how-to)
• Read the reference below to find out how to generate domain keys and add public key to the domain's DNS records

Reference

• Postfix SASL Howto
• How To Install and Configure DKIM with Postfix on Debian Wheezy
• Based on catatnight/docker-postfix