Docker Mailserver

A fullstack but simple mail server (SMTP, IMAP, LDAP, Antispam, Antivirus, etc.). Only configuration files, no SQL database. Keep it simple and versioned. Easy to deploy and upgrade. Documentation via MkDocs. Why this image was created..

If you have issues, read the full README and the documentation for your version (default is edge) first before opening an issue. The issue tracker is for issues, not for personal support.

1. Included Services
2. Issues and Contributing
3. Requirements
4. Usage
5. Examples
6. Environment Variables
7. Documentation
8. Release Notes

Included Services

• Postfix with SMTP or LDAP auth
• Dovecot for SASL, IMAP (or POP3), with LDAP Auth, Sieve and quotas
• Amavis
• SpamAssassin supporting custom rules
• ClamAV with automatic updates
• OpenDKIM
• OpenDMARC
• Fail2ban
• Fetchmail
• Postscreen
• Postgrey
• LetsEncrypt and self-signed certificates
• Setup script to easily configure and maintain your mailserver
• Basic Sieve support using dovecot
• SASLauthd with LDAP auth
• Persistent data and state
• CI/CD
• Extension Delimiters (you+extension@example.com go to you@example.com)

Requirements

Recommended:

• 1 Core
• 2GB RAM
• Swap enabled for the container

Minimum:

• 1 vCore
• 512MB RAM

Note: You'll need to deactivate some services like ClamAV to be able to run on a host with 512MB of RAM. Even with 1G RAM you may run into problems without swap, see FAQ.

Usage

Available image sources / tags

CI/CD will automatically build, test and push new images to container registries. Currently, the following registries are supported:

• DockerHub
• GitHub Container Registry

All workflows are using the tagging convention listed below. It is subsequently applied to all images pushed to supported container registries:

Event	Ref	Commit SHA	Image Tags
push	refs/heads/master	cf20257	edge
push	refs/heads/stable	cf20257	stable
push tag	refs/tags/[v]1.2.3	ad132f5	1.2.3, 1.2, 1, latest

Get the tools

Download docker-compose.yml and mailserver.env

wget https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/master/docker-compose.yml
wget https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/master/mailserver.env

and the setup.sh in the correct version

# if you're using :edge as the image tag
wget https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/master/setup.sh
# if you're using :latest (= :9.1.0) as the image tag
wget https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/v9.1.0/setup.sh

chmod a+x ./setup.sh

# and make yourself familiar with the script
./setup.sh help

Make sure to get the setup.sh that comes with the release you're using. Look up the release and the git commit on which this release is based upon by selecting the appropriate tag on GitHub. This can done with the "Switch branches/tags" button on GitHub, choosing the right tag. This is done in order to rule out possible inconsistencies between versions.

Create a docker-compose environment

1. Install the latest docker-compose
2. Edit docker-compose.yml to your liking
   • substitute <HOSTNAME> and <DOMAINNAME> according to your domain
   • if you want to use SELinux for the ./config/:/tmp/docker-mailserver/ mount, append -z or -Z
3. Configure the mailserver container to your liking by editing mailserver.env (Documentation)
   • this file supports only simple VAR=VAL (don't quote your values)
   • variable substitution is not supported (e.g. 🚫OVERRIDE_HOSTNAME=$HOSTNAME.$DOMAINNAME 🚫)

Get up and running

docker-compose up -d mailserver

# for SELinux, use -Z 
./setup.sh [-Z] email add <user@domain> [<password>]
./setup.sh [-Z] alias add postmaster@<domain> <user@domain>
./setup.sh [-Z] config dkim

If you're seeing error messages about unchecked error, please verify that you're using the right version of setup.sh. Refer to the Get the tools section and / or execute ./setup.sh help and read the VERSION section.

In case you're using LDAP, the setup looks a bit different as you do not add user accounts directly. Postfix doesn't know your domain(s) and you need to provide it when configuring DKIM:

./setup.sh config dkim domain '<domain.tld>[,<domain2.tld>]'

If you want to see detailed usage information, run ./setup.sh config dkim help.

Miscellaneous

DNS - DKIM

When keys are generated, you can configure your DNS server by just pasting the content of config/opendkim/keys/domain.tld/mail.txt to set up DKIM. See the documentation for more details.

Custom user changes & patches

If you'd like to change, patch or alter files or behavior of docker-mailserver, you can use a script. See the documentation for a detailed explanation.

Updating docker-mailserver

docker-compose pull
docker-compose down
docker-compose up -d mailserver

You're done! And don't forget to have a look at the remaining functions of the setup.sh script with ./setup.sh help.

Supported Operating Systems

We are currently providing support for Linux. Windows is not supported and is known to cause problems. Similarly, macOS is not officially supported - but you may get it to work there. In the end, Linux should be your preferred operating system for this image, especially when using this mailserver in production.

Bare Domains

If you want to use a bare domain (hostname == domainname), see FAQ.

Support for Multiple Domains

docker-mailserver supports multiple domains out of the box, so you can do this:

./setup.sh email add user1@docker.example.com
./setup.sh email add user1@mail.example.de
./setup.sh email add user1@server.example.org

SPF/Forwarding Problems

If you got any problems with SPF and/or forwarding mails, give SRS a try. You enable SRS by setting ENABLE_SRS=1. See the variable description for further information.

Ports

See the documentation for further details and best practice advice, especially regarding security concerns.

Examples

With Relevant Environmental Variables

This example provides you only with a basic example of what a minimal setup could look like. We strongly recommend that you go through the configuration file yourself and adjust everything to your needs. The default docker-compose.yml can be used for the purpose out-of-the-box, see the usage section.

version: '3.8'

services:
  mailserver:
    image: docker.io/mailserver/docker-mailserver:latest
    hostname: mail
    domainname: example.com
    container_name: mailserver
    ports:
      - "25:25"
      - "143:143"
      - "587:587"
      - "993:993"
    volumes:
      - maildata:/var/mail
      - mailstate:/var/mail-state
      - maillogs:/var/log/mail
      - ./config/:/tmp/docker-mailserver/
    environment:
      - ENABLE_SPAMASSASSIN=1
      - SPAMASSASSIN_SPAM_TO_INBOX=1
      - ENABLE_CLAMAV=1
      - ENABLE_FAIL2BAN=1
      - ENABLE_POSTGREY=1
      - ENABLE_SASLAUTHD=0
      - ONE_DIR=1
      - DMS_DEBUG=0
    cap_add:
      - NET_ADMIN
      - SYS_PTRACE
    restart: always

volumes:
  maildata:
  mailstate:
  maillogs:

LDAP setup

version: '3.8'

services:
  mailserver:
    image: docker.io/mailserver/docker-mailserver:latest
    hostname: mail
    domainname: example.com
    container_name: mailserver
    ports:
      - "25:25"
      - "143:143"
      - "587:587"
      - "993:993"
    volumes:
      - maildata:/var/mail
      - mailstate:/var/mail-state
      - maillogs:/var/log/mail
      - ./config/:/tmp/docker-mailserver/
    environment:
      - ENABLE_SPAMASSASSIN=1
      - SPAMASSASSIN_SPAM_TO_INBOX=1
      - ENABLE_CLAMAV=1
      - ENABLE_FAIL2BAN=1
      - ENABLE_POSTGREY=1
      - ONE_DIR=1
      - DMS_DEBUG=0
      - ENABLE_LDAP=1
      - LDAP_SERVER_HOST=ldap # your ldap container/IP/ServerName
      - LDAP_SEARCH_BASE=ou=people,dc=localhost,dc=localdomain
      - LDAP_BIND_DN=cn=admin,dc=localhost,dc=localdomain
      - LDAP_BIND_PW=admin
      - LDAP_QUERY_FILTER_USER=(&(mail=%s)(mailEnabled=TRUE))
      - LDAP_QUERY_FILTER_GROUP=(&(mailGroupMember=%s)(mailEnabled=TRUE))
      - LDAP_QUERY_FILTER_ALIAS=(|(&(mailAlias=%s)(objectClass=PostfixBookMailForward))(&(mailAlias=%s)(objectClass=PostfixBookMailAccount)(mailEnabled=TRUE)))
      - LDAP_QUERY_FILTER_DOMAIN=(|(&(mail=*@%s)(objectClass=PostfixBookMailAccount)(mailEnabled=TRUE))(&(mailGroupMember=*@%s)(objectClass=PostfixBookMailAccount)(mailEnabled=TRUE))(&(mailalias=*@%s)(objectClass=PostfixBookMailForward)))
      - DOVECOT_PASS_FILTER=(&(objectClass=PostfixBookMailAccount)(uniqueIdentifier=%n))
      - DOVECOT_USER_FILTER=(&(objectClass=PostfixBookMailAccount)(uniqueIdentifier=%n))
      - ENABLE_SASLAUTHD=1
      - SASLAUTHD_MECHANISMS=ldap
      - SASLAUTHD_LDAP_SERVER=ldap
      - SASLAUTHD_LDAP_BIND_DN=cn=admin,dc=localhost,dc=localdomain
      - SASLAUTHD_LDAP_PASSWORD=admin
      - SASLAUTHD_LDAP_SEARCH_BASE=ou=people,dc=localhost,dc=localdomain
      - SASLAUTHD_LDAP_FILTER=(&(objectClass=PostfixBookMailAccount)(uniqueIdentifier=%U))
      - POSTMASTER_ADDRESS=postmaster@localhost.localdomain
      - POSTFIX_MESSAGE_SIZE_LIMIT=100000000
    cap_add:
      - NET_ADMIN
      - SYS_PTRACE
    restart: always

volumes:
  maildata:
  mailstate:
  maillogs: