docker-mailserver

A fullstack but simple mail server (smtp, imap, antispam, antivirus...). Only configuration files, no SQL database. Keep it simple and versioned. Easy to deploy and upgrade.

Includes:

• postfix with smtp or ldap auth
• dovecot for sasl, imap (and optional pop3) with ssl support, with ldap auth
• saslauthd with ldap auth
• amavis
• spamassasin supporting custom rules
• clamav with automatic updates
• opendkim
• opendmarc
• fail2ban
• fetchmail
• postgrey
• basic sieve support using dovecot
• LetsEncrypt and self-signed certificates
• persistent data and state (but think about backups!)
• integration tests
• automated builds on docker hub

Why I created this image: Simple mail server with Docker

Before you open an issue, please have a look this README, the Wiki and Postfix/Dovecot documentation.

Requirements

Recommended:

• 1 CPU
• 1GB RAM

Minimum:

• 1 CPU
• 512MB RAM

Note: You'll need to deactivate some services like ClamAV to be able to run on a host with 512MB of RAM.

Usage

Get latest image

docker pull tvial/docker-mailserver:latest

Create a docker-compose.yml

Adapt this file with your FQDN. Install docker-compose in the version 1.6 or higher.

Your configs must be mounted in /tmp/docker-mailserver/. To understand how things work on boot, please have a look to start-mailserver.sh

restart: always ensures that the mail server container (and ELK container when using the mail server together with ELK stack) is automatically restarted by Docker in cases like a Docker service or host restart or container exit.

version: '2'

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

volumes:
  maildata:
    driver: local
  mailstate:
    driver: local

for ldap setup:

version: '2'

services:
  mail:
    image: tvial/docker-mailserver:latest
    hostname: mail
    domainname: domain.com
    container_name: mail
    ports:
      - "25:25"
      - "143:143"
      - "587:587"
      - "993:993"
    volumes:
      - maildata:/var/mail
      - mailstate:/var/mail-state
      - ./config/:/tmp/docker-mailserver/
    environment:
      - ENABLE_SPAMASSASSIN=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)(mailEnabled=TRUE))"
      - 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
      - POSTMASTER_ADDRESS=postmaster@localhost.localdomain
    cap_add:
      - NET_ADMIN
      - SYS_PTRACE

volumes:
  maildata:
    driver: local
  mailstate:
    driver: local

Create your mail accounts

Don't forget to adapt MAIL_USER and MAIL_PASS to your needs

mkdir -p config
touch config/postfix-accounts.cf
docker run --rm \
  -e MAIL_USER=user1@domain.tld \
  -e MAIL_PASS=mypassword \
  -ti tvial/docker-mailserver:latest \
  /bin/sh -c 'echo "$MAIL_USER|$(doveadm pw -s SHA512-CRYPT -u $MAIL_USER -p $MAIL_PASS)"' >> config/postfix-accounts.cf

Generate DKIM keys

docker run --rm \
  -v "$(pwd)/config":/tmp/docker-mailserver \
  -ti tvial/docker-mailserver:latest generate-dkim-config

This generates DKIM keys for domains in configuration files. You can also generate DKIM key for a domain by using command

docker run --rm \
  -v "$(pwd)/config":/tmp/docker-mailserver \
  -ti tvial/docker-mailserver:latest generate-dkim-domain name_of_domain

Now the keys are generated, you can configure your DNS server by just pasting the content of config/opendkim/keys/domain.tld/mail.txt in your domain.tld.hosts zone.

Note: you can also manage email accounts, DKIM keys and more with the setup.sh convenience script.

Start the container

docker-compose up -d mail

You're done!

Environment variables

Please check how the container starts to understand what's expected. Also if an option doesn't work as documented here, check if you are running the latest image!

Value in bold is the default value.

DMS_DEBUG

• 0 => Debug disabled
• 1 => Enables debug on startup

ENABLE_CLAMAV

• 0 => Clamav is disabled
• 1 => Clamav is enabled

ENABLE_SPAMASSASSIN

• 0 => Spamassassin is disabled
• 1 => Spamassassin is enabled

SA_TAG

• 2.0 => add spam info headers if at, or above that level

Note: this spamassassin setting needs ENABLE_SPAMASSASSIN=1

SA_TAG2

• 6.31 => add 'spam detected' headers at that level

Note: this spamassassin setting needs ENABLE_SPAMASSASSIN=1

SA_KILL

• 6.31 => triggers spam evasive actions

Note: this spamassassin setting needs ENABLE_SPAMASSASSIN=1

SA_SPAM_SUBJECT

• ***SPAM*** => add tag to subject if spam detected

Note: this spamassassin setting needs ENABLE_SPAMASSASSIN=1

ONE_DIR

• 0 => state in default directories
• 1 => consolidate all states into a single directory (/var/mail-state) to allow persistence using docker volumes

ENABLE_POP3

• empty => POP3 service disabled
• 1 => Enables POP3 service

ENABLE_FAIL2BAN

• 0 => fail2ban service disabled
• 1 => Enables fail2ban service

If you enable Fail2Ban, don't forget to add the following lines to your docker-compose.yml:

cap_add:
  - NET_ADMIN

Otherwise, iptables won't be able to ban IPs.

ENABLE_MANAGESIEVE

• empty => Managesieve service disabled
• 1 => Enables Managesieve on port 4190

ENABLE_FETCHMAIL

• 0 => fetchmail disabled
• 1 => fetchmail enabled

FETCHMAIL_POLL

• 300 => fetchmail The number of seconds for the interval

ENABLE_LDAP

• empty => LDAP authentification is disabled
• 1 => LDAP authentification is enabled
• NOTE:
  • A second container for the ldap service is necessary (e.g. docker-openldap)
  • For preparing the ldap server to use in combination with this continer this article may be helpful

LDAP_START_TLS

• empty => no
• yes => LDAP over TLS enabled for Postfix

LDAP_SERVER_HOST

• empty => mail.domain.com
• => Specify the dns-name/ip-address where the ldap-server
• NOTE: If you going to use the mailserver in combination with docker-compose you can set the service name here

LDAP_SEARCH_BASE

• empty => ou=people,dc=domain,dc=com
• => e.g. LDAP_SEARCH_BASE=dc=mydomain,dc=local

LDAP_BIND_DN

• empty => cn=admin,dc=domain,dc=com
• => take a look at examples of SASL_LDAP_BIND_DN

LDAP_BIND_PW

• empty => admin
• => Specify the password to bind against ldap

LDAP_QUERY_FILTER_USER

• e.g. "(&(mail=%s)(mailEnabled=TRUE))"
• => Specify how ldap should be asked for users

LDAP_QUERY_FILTER_GROUP

• e.g. "(&(mailGroupMember=%s)(mailEnabled=TRUE))"
• => Specify how ldap should be asked for groups

LDAP_QUERY_FILTER_ALIAS

• e.g. "(&(mailAlias=%s)(mailEnabled=TRUE))"
• => Specify how ldap should be asked for aliases

DOVECOT_TLS

• empty => no
• yes => LDAP over TLS enabled for Dovecot

DOVECOT_USER_FILTER

• e.g. "(&(objectClass=PostfixBookMailAccount)(uniqueIdentifier=%n))"

DOVECOT_PASS_FILTER

• e.g. "(&(objectClass=PostfixBookMailAccount)(uniqueIdentifier=%n))"

OVERRIDE_HOSTNAME

• empty => uses the hostname command to get the mail server's canonical hostname
• => Specify a fully-qualified domainname to serve mail for. This is used for many of the config features so if you can't set your hostname (e.g. you're in a container platform that doesn't let you) specify it in this environment variable.

POSTMASTER_ADDRESS

• empty => postmaster@domain.com
• => Specify the postmaster address

ENABLE_POSTGREY

• 0 => postgrey is disabled
• 1 => postgrey is enabled

POSTGREY_DELAY

• 300 => greylist for N seconds

Note: This postgrey setting needs ENABLE_POSTGREY=1

POSTGREY_MAX_AGE

• 35 => delete entries older than N days since the last time that they have been seen

Note: This postgrey setting needs ENABLE_POSTGREY=1

POSTGREY_TEXT

• Delayed by postgrey => response when a mail is greylisted

Note: This postgrey setting needs ENABLE_POSTGREY=1

ENABLE_SASLAUTHD

• 0 => saslauthd is disabled
• 1 => saslauthd is enabled

SASLAUTHD_MECHANISMS

• empty => pam
• ldap => authenticate against ldap server
• shadow => authenticate against local user db
• mysql => authenticate against mysql db
• rimap => authenticate against imap server
• NOTE: can be a list of mechanisms like pam ldap shadow

SASLAUTHD_MECH_OPTIONS

• empty => None
• e.g. with SASLAUTHD_MECHANISMS rimap you need to specify the ip-address/servername of the imap server ==> xxx.xxx.xxx.xxx

SASLAUTHD_LDAP_SERVER

• empty => localhost

SASLAUTHD_LDAP_SSL

• empty or 0 => ldap:// will be used
• 1 => ldaps:// will be used

SASLAUTHD_LDAP_BIND_DN

• empty => anonymous bind
• specify an object with priviliges to search the directory tree
• e.g. active directory: SASLAUTHD_LDAP_BIND_DN=cn=Administrator,cn=Users,dc=mydomain,dc=net
• e.g. openldap: SASLAUTHD_LDAP_BIND_DN=cn=admin,dc=mydomain,dc=net

SASLAUTHD_LDAP_PASSWORD

• empty => anonymous bind

SASLAUTHD_LDAP_SEARCH_BASE

• empty => Reverting to SASLAUTHD_MECHANISMS pam
• specify the search base

SASLAUTHD_LDAP_FILTER

• empty => default filter (&(uniqueIdentifier=%u)(mailEnabled=TRUE))
• e.g. for active directory: (&(sAMAccountName=%U)(objectClass=person))
• e.g. for openldap: (&(uid=%U)(objectClass=person))

SASL_PASSWD

• empty => No sasl_passwd will be created
• string => /etc/postfix/sasl_passwd will be created with the string as password

SMTP_ONLY

• empty => all daemons start
• 1 => only launch postfix smtp

SSL_TYPE

• empty => SSL disabled
• letsencrypt => Enables Let's Encrypt certificates
• custom => Enables custom certificates
• manual => Let's you manually specify locations of your SSL certificates for non-standard cases
• self-signed => Enables self-signed certificates

Please read the SSL page in the wiki for more information.

PERMIT_DOCKER

Set different options for mynetworks option (can be overwrite in postfix-main.cf)

• empty => localhost only
• host => Add docker host (ipv4 only)
• network => Add all docker containers (ipv4 only)

VIRUSMAILS_DELETE_DELAY

Set how many days a virusmail will stay on the server before being deleted

• empty => 7 days

ENABLE_POSTFIX_VIRTUAL_TRANSPORT

This Option is activating the Usage of POSTFIX_DAGENT to specify a ltmp client different from default dovecot socket.

• empty => disabled
• 1 => enabled

POSTFIX_DAGENT

Enabled by ENABLE_POSTFIX_VIRTUAL_TRANSPORT. Specify the final delivery of postfix

• empty: fail
• lmtp:unix:private/dovecot-lmtp (use socket)
• lmtps:inet:<host>:<port> (secure lmtp with starttls, take a look at https://sys4.de/en/blog/2014/11/17/sicheres-lmtp-mit-starttls-in-dovecot/)
• lmtp:<kopano-host>:2003 (use kopano as mailstore)
• etc.