Docker Mailserver

A production-ready 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.

Originally created by @tomav, docker-mailserver is now maintained by volunteers since January 2021.

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 mail-server
• Basic Sieve support using dovecot
• SASLauthd with LDAP auth (please see the note down below)
• 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
• 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 Images / Tags - Tagging Convention

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

1. DockerHub
2. GitHub Container Registry

All workflows are using the tagging convention listed below. It is subsequently applied to all images.

Event	Image Tags
push on master	edge
push tag	1.2.3, 1.2, 1, latest

Get the Tools

Since Docker Mailserver v10.2.0, setup.sh functionality is included within the container image. The external convenience script is no longer required if you prefer using docker exec <CONTAINER NAME> setup <COMMAND> instead. If you're new to docker-mailserver, it is recommended to use the script setup.sh for convenience.

DMS_GITHUB_URL='https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/master'
wget "${DMS_GITHUB_URL}/docker-compose.yml"
wget "${DMS_GITHUB_URL}/mailserver.env"
wget "${DMS_GITHUB_URL}/setup.sh"
chmod a+x ./setup.sh

Create a docker-compose Environment

1. Install the latest docker-compose
2. Edit docker-compose.yml to your liking
   • substitute mail (hostname) and example.com (domainname) according to your FQDN
   • if you want to use SELinux for the ./docker-data/dms/config/:/tmp/docker-mailserver/ mount, append -z or -Z
3. Configure the mailserver container to your liking by editing mailserver.env (Documentation), but keep in mind this .env file:
   • only basic VAR=VAL is supported (do not quote your values!)
   • variable substitution is not supported (e.g. 🚫 OVERRIDE_HOSTNAME=$HOSTNAME.$DOMAINNAME 🚫)

Note: If you're using podman, make sure to read the related documentation

Get up and running

First Things First

Use docker-compose up / down, not docker-compose start / stop. Otherwise, the container is not properly destroyed and you may experience problems during startup because of inconsistent state.

You are able to get a full overview of how the configuration works by either running:

1. ./setup.sh help which includes the options of setup.sh.
2. docker run --rm docker.io/mailserver/docker-mailserver:latest setup help which provides you with all the information on configuration provided "inside" the container itself.

If no docker-mailserver container is running, any ./setup.sh command will check online for the :latest image tag (the current stable release), performing a docker pull ... if necessary followed by running the command in a temporary container.

$ ./setup.sh help
Image 'docker.io/mailserver/docker-mailserver:latest' not found. Pulling ...
SETUP(1)

NAME
    setup - 'docker-mailserver' Administration & Configuration script
...

$ docker run --rm docker.io/mailserver/docker-mailserver:latest setup help
SETUP(1)

NAME
    setup - 'docker-mailserver' Administration & Configuration script
...

Starting for the first time

On first start, you will need to add at least one email account (unless you're using LDAP). You have two minutes to do so, otherwise DMS will shutdown and restart. You can add accounts with the following two methods:

1. Use setup.sh: ./setup.sh email add <user@domain>
2. Run the command directly in the container: docker exec -ti <CONTAINER NAME> setup email add <user@domain>

You can then proceed by creating the postmaster alias and by creating DKIM keys.

docker-compose up -d mailserver

# you may add some more users
# for SELinux, use -Z
./setup.sh [-Z] email add <user@domain> [<password>]

# and configure aliases, DKIM and more
./setup.sh [-Z] alias add postmaster@<domain> <user@domain>

Miscellaneous

DNS - DKIM

You can (and you should) generate DKIM keys by running

./setup.sh [-Z] config dkim

If you want to see detailed usage information, run

./setup.sh config dkim help

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>]'

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

Make sure to read the CHANGELOG before updating to new versions, to be prepared for possible breaking changes.

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

You should see the new version number on startup, for example: [ TASKLOG ] Welcome to docker-mailserver 10.1.2.

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 mail-server 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.

Mailboxes (aka IMAP Folders)

INBOX is setup by default with the special IMAP folders Drafts, Sent, Junk and Trash. You can learn how to modify or add your own folders (including additional special folders like Archive) by visiting our docs page Customizing IMAP Folders for more information.

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
    container_name: mailserver
    hostname: mail
    domainname: example.com
    ports:
      - "25:25"
      - "143:143"
      - "587:587"
      - "993:993"
    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
    environment:
      - ENABLE_SPAMASSASSIN=1
      - SPAMASSASSIN_SPAM_TO_INBOX=1
      - ENABLE_CLAMAV=1
      - ENABLE_FAIL2BAN=1
      - ENABLE_POSTGREY=1
      - ENABLE_SASLAUTHD=0
      - ONE_DIR=1
    cap_add:
      - NET_ADMIN
      - SYS_PTRACE
    restart: always

LDAP Setup

Note There are currently no LDAP maintainers. If you encounter issues, please raise them in the issue tracker, but be aware that the core maintainers team will most likely not be able to help you. We would appreciate and we encourage everyone to actively participate in maintaining LDAP-related code by becoming a maintainer!

version: '3.8'

services:
  mailserver:
    image: docker.io/mailserver/docker-mailserver:latest
    container_name: mailserver
    hostname: mail
    domainname: example.com
    ports:
      - "25:25"
      - "143:143"
      - "587:587"
      - "993:993"
    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
    environment:
      - ENABLE_SPAMASSASSIN=1
      - SPAMASSASSIN_SPAM_TO_INBOX=1
      - ENABLE_CLAMAV=1
      - ENABLE_FAIL2BAN=1
      - ENABLE_POSTGREY=1
      - ONE_DIR=1
      - 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