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
• postscreen
• postgrey
• basic sieve support using dovecot
• LetsEncrypt and self-signed certificates
• setup script to easily configure and maintain your mailserver
• 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

Get the tools

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

curl -o setup.sh https://raw.githubusercontent.com/tomav/docker-mailserver/master/setup.sh; chmod a+x ./setup.sh

curl -o docker-compose.yml https://raw.githubusercontent.com/tomav/docker-mailserver/master/docker-compose.yml.dist

curl -o .env https://raw.githubusercontent.com/tomav/docker-mailserver/master/.env.dist

Create a docker-compose environment

• Edit the .env to your liking. Adapt this file with your FQDN.
• Install docker-compose in the version 1.6 or higher.

Create your mail accounts

./setup.sh email add <user@domain> [<password>]

Generate DKIM keys

./setup.sh config dkim

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.

Start the container

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

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.

For informational purposes:

Your config folder will be mounted in /tmp/docker-mailserver/. To understand how things work on boot, please have a look at 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.

Exposed ports

• 25 receiving email from other mailservers
• 465 SSL Client email submission
• 587 TLS Client email submission
• 143 StartTLS IMAP client
• 993 TLS/SSL IMAP client
• 110 POP3 client
• 995 TLS/SSL POP3 client

Note: Port 25 is only for receiving email from other mailservers and not for submitting email. You need to use port 465 or 587 for this.

Examples with just the relevant environmental variables:

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

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.

General

DMS_DEBUG

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

ENABLE_CLAMAV

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

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.

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.

TLS_LEVEL

• empty => modern
• modern => Enables TLSv1.2 and modern ciphers only. (default)
• intermediate => Enables TLSv1, TLSv1.1 and TLSv1.2 and broad compatibility ciphers.
• old => NOT implemented. If you really need it, then customize the TLS ciphers overriding postfix and dovecot settings [ wiki](https://github.com/tomav/docker-mailserver/wiki/

SPOOF_PROTECTION

Configures the handling of creating mails with forged sender addresses.

• empty => Mail address spoofing allowed. Any logged in user may create email messages with a forged sender address. See also Wikipedia(not recommended, but default for backwards compatibility reasons)
• 1 => (recommended) Mail spoofing denied. Each user may only send with his own or his alias addresses. Addresses with extension delimiters are not able to send messages.

ENABLE_SRS

Enables the Sender Rewriting Scheme. SRS is needed if your mail server acts as forwarder. See postsrsd for further explanation.

• 0 => Disabled
• 1 => Enabled

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.

ENABLE_MANAGESIEVE

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

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

POSTSCREEN_ACTION

• enforce => Allow other tests to complete. Reject attempts to deliver mail with a 550 SMTP reply, and log the helo/sender/recipient information. Repeat this test the next time the client connects.
• drop => Drop the connection immediately with a 521 SMTP reply. Repeat this test the next time the client connects.
• ignore => Ignore the failure of this test. Allow other tests to complete. Repeat this test the next time the client connects. This option is useful for testing and collecting statistics without blocking mail.

REPORT_RECIPIENT

Enables a report being sent (created by pflogsumm) on a regular basis.

• 0 => Report emails are disabled
• 1 => Using POSTMASTER_ADDRESS as the recipient
• => Specify the recipient address

REPORT_INTERVAL

changes the interval in which a report is being sent.

• daily => Send a daily report
• weekly => Send a report every week
• monthly => Send a report every month

Note: This Variable actually controls logrotate inside the container and rotates the log depending on this setting. The main log output is still available in its entirety via docker logs mail (Or your respective container name). If you want to control logrotation for the docker generated logfile see: Docker Logging Drivers

Spamassassin

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

Fetchmail

ENABLE_FETCHMAIL

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

FETCHMAIL_POLL

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

LDAP

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

DOVECOT_USER_FILTER

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

DOVECOT_PASS_FILTER

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

Postgrey

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

SASL Auth

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

SRS (Sender Rewriting Scheme)

SRS_EXCLUDE_DOMAINS

• empty => Envelope sender will be rewritten for all domains
• provide comma seperated list of domains to exclude from rewriting

SRS_SECRET

• empty => generated when the container is started for the first time
• provide a secret to use in base64
• you may specify multiple keys, comma separated. the first one is used for signing and the remaining will be used for verification. this is how you rotate and expire keys
• if you have a cluster/swarm make sure the same keys are on all nodes
• example command to generate a key: dd if=/dev/urandom bs=24 count=1 2>/dev/null | base64

Multi-domain Relay Hosts

RELAY_HOST

• empty => don't configure relay host
• default host to relay mail through

RELAY_PORT

• empty => 25
• default port to relay mail through

RELAY_USER

• empty => no default
• default relay username (if no specific entry exists in postfix-sasl-password.cf)

RELAY_PASSWORD

• empty => no default
• password for default relay user