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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.

Why this image was created.

Included Services
Opening Issues and Contributing
Requirements
Usage
Examples
Environment Variables
Release Notes

Included Services

Postfix with SMTP or LDAP auth
Dovecot for SASL, IMAP (or POP3), with LDAP Auth, Sieve and quotas
Amavis
Spamassasin 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)

Opening Issues and Contributing

Before opening an issue, read this README carefully, use the Wiki, the Postfix/Dovecot documentation and your search engine you trust. The issue tracker is not meant to be used for unrelated questions! If you'd like to contribute, read CONTRIBUTING.md thoroughly.

Requirements

Recommended:

1 Core
1-2GB 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

Get the tools

Download the docker-compose.yml, compose.env, mailserver.env and the setup.sh files:

wget https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/stable/setup.sh
wget https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/stable/docker-compose.yml
wget https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/stable/mailserver.env
wget -O .env https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/stable/compose.env

chmod a+x ./setup.sh

Create a docker-compose environment

Install the latest docker-compose
Edit the files .env and mailserver.env to your liking:
- .env contains the configuration for Docker Compose
- mailserver.env contains the configuration for the mailserver container
- these files supports only simple VAR=VAL
- don't quote your values
- variable substitution is not supported (e.g. OVERRIDE_HOSTNAME=$HOSTNAME.$DOMAINNAME).
Variables in .env are expanded in the docker-compose.yml file only and not in the container. The file mailserver.env serves this case where environment variables are used in the container.
If you want to use a bare domain (host name = domain name), see FAQ

Get up and running

If you'd like to use SELinux, add -Z to the variable SELINUX_LABEL in .env. If you want the volume bind mount to be shared among other containers switch -Z to -z

docker-compose up -d mail

# without SELinux
./setup.sh email add <user@domain> [<password>]
./setup.sh alias add postmaster@<domain> <user@domain>
./setup.sh config dkim

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

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.

Custom user changes & patches

If you'd like to change, patch or alter files or behavior of docker-mailserver, you can use a script. Just place it the config/ folder that is created on startup and call it user-patches.sh. The setup is done like this:

# 1. Either create the config/ directory yourself
#    or let docker-mailserver create it on initial
#    startup
/where/docker-mailserver/resides/ $ mkdir config && cd config

# 2. Create the user-patches.sh script and make it
#    executable
/where/docker-mailserver/resides/config/ $ touch user-patches.sh
/where/docker-mailserver/resides/config/ $ chmod +x user-patches.sh

# 3. Edit it
/where/docker-mailserver/resides/config/ $ vi user-patches.sh
/where/docker-mailserver/resides/config/ $ cat user-patches.sh
#! /bin/bash

# ! THIS IS AN EXAMPLE !

# If you modify any supervisord configuration, make sure
# to run "supervisorctl update" afterwards.

set -euo pipefail
echo 'user-patches.sh started'

if ! grep '192.168.0.1' /etc/hosts
then
  echo -e '192.168.0.1 some.domain.com' >> /etc/hosts
fi

echo 'user-patches.sh finished successfully'

And you're done. The user patches script runs right before starting daemons. That means, all the other configuration is in place, so the script can make final adjustments.

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.

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

Updating `docker-mailserver`

docker-compose down
docker pull docker.io/mailserver/docker-mailserver:<VERSION TAG>
docker-compose up -d mail

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

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.

Exposed ports

Protocol	Opt-in Encryption ¹	Enforced Encryption	Purpose
SMTP	25	N/A	Transfer²
ESMTP	587	465³	Submission
POP3	110	995	Retrieval
IMAP4	143	993	Retrieval

A connection may be secured over TLS when both ends support STARTTLS. On ports 110, 143 and 587, docker-mailserver will reject a connection that cannot be secured. Port 25 is required to support insecure connections.
Receives email and filters for spam and viruses. For submitting outgoing mail you should prefer the submission ports(465, 587), which require authentication. Unless a relay host is configured, outgoing email will leave the server via port 25(thus outbound traffic must not be blocked by your provider or firewall).
A submission port since 2018, RFC 8314. Originally a secure variant of port 25.

See the wiki 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:
  mail:
    image: docker.io/mailserver/docker-mailserver:latest
    hostname: mail          # ${HOSTNAME}
    domainname: domain.com  # ${DOMAINNAME}
    container_name: mail    # ${CONTAINER_NAME}
    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:
  mail:
    image: docker.io/mailserver/docker-mailserver:latest
    hostname: mail          # ${HOSTNAME}
    domainname: domain.com  # ${DOMAINNAME}
    container_name: mail    # ${CONTAINER_NAME}
    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:

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