hardware/mailserver

Build

Docker image

Simple and full-featured mail server as a set of multiple docker images includes :

• Postfix : a full set smtp email server supporting custom rules
• Dovecot : secure imap and pop3 email server
• Amavis : content filter implementing decoding, processing and checking e-mails
• Spamassasin : anti-spam filter
• Clamav : antivirus with automatic updates
• OpenDKIM : implementation of DKIM (Domain Keys Identified Mail)
• OpenDMARC : implementation of DMARC (Domain-based Message Authentication, Reporting & Conformance)
• Sieve : email filtering (vacation auto-responder, auto-forward...etc)
• Fetchmail : fetch e-mails from external IMAP/POP3 server into local mailbox
• Postgrey : greylisting policy server
• Gross : greylisting of suspicious sources
• Rainloop : web based email client
• Postfixadmin : web based administration interface
• NSD : authoritative DNS server with DNSSEC support
• Nginx : web server with HTTP/2 and TLS 1.3 (DRAFT), statically linked against BoringSSL
• SSL : lets encrypt and self-signed certificates support
• Supporting multiple virtual domains over MySQL backend
• Integration tests with Travis CI
• Automated builds on DockerHub

How to use

1 - Get latest image

# Pull from hub.docker.com :
docker pull hardware/mailserver

# or build it manually :
docker build -t hardware/mailserver https://github.com/hardware/mailserver.git#master

2 - Get latest docker-compose.yml

See docker-compose.sample.yml

Note : Change your hostname / domain name, and adapt to your needs

3 - Reverse proxy setup

See Reverse proxy configuration

Start the mailstack :

docker-compose up -d

4 - Control panel setup / virtual domains and mailboxes creation

See Postfixadmin initial configuration

5 - Webmail setup (optional)

See Rainloop initial configuration

6 - DNS records

HOSTNAME            CLASS             RECORD TYPE          VALUE
------------------------------------------------------------------------------------------------
mail                IN                A                    SERVER_IPV4
@                   IN                MX          10       mail.domain.tld.
@                   IN                TXT                  "v=spf1 a mx ip4:SERVER_IPV4 ~all"
mail._domainkey     IN                TXT                  "v=DKIM1; k=rsa; p=DKIM Public Key"
_dmarc              IN                TXT                  "v=DMARC1; p=reject; rua=mailto:[email protected]; ruf=mailto:[email protected]; fo=0; adkim=s; aspf=s; pct=100; rf=afrf; sp=reject"

The DKIM public key is available on host here : /mnt/docker/mail/opendkim/domain.tld/mail.txt

See NSD initial configuration, if you want to setup your own authoritative dns server with dnssec support 🔒

You can audit your mailserver with the following assessment services :

• https://www.mail-tester.com/
• https://observatory.mozilla.org/
• https://www.hardenize.com/

7 - Done, congratulation ! 🎉

At first launch, the container takes few minutes to generate SSL certificates (if needed), Diffie-Hellman parameters, DKIM keypair and update clamav database, all of this takes some time, be patient...

You can check startup logs with this command :

docker logs -f mailserver

Environment variables

Variable	Description	Type	Default value
VMAILUID	vmail user id	optional	1024
VMAILGID	vmail group id	optional	1024
VMAIL_SUBDIR	Individual mailbox' subdirectory	optional	mail
OPENDKIM_KEY_LENGTH	Size of your DKIM RSA key pair	optional	2048
DBHOST	MariaDB instance ip/hostname	optional	mariadb
DBUSER	MariaDB database username	optional	postfix
DBNAME	MariaDB database name	optional	postfix
DBPASS	MariaDB database password	required	null
ADD_DOMAINS	Add additional domains to the mailserver separated by commas (needed for dkim keys etc.)	optional	null
DISABLE_CLAMAV	Disable virus scanning	optional	false
DISABLE_SPAMASSASSIN	Disable SPAM checking	optional	false
DISABLE_SIEVE	Disable ManageSieve protocol	optional	false
GREYLISTING	Enable greylisting policy server	optional	off
ENABLE_POP3	Enable POP3 protocol	optional	false
ENABLE_FETCHMAIL	Enable fetchmail forwarding	optional	false
FETCHMAIL_INTERVAL	Fetchmail polling interval	optional	10
RECIPIENT_DELIMITER	RFC 5233 subaddress extension separator (single character only)	optional	+

If DISABLE_CLAMAV and DISABLE_SPAMASSASSIN are both set to true, Amavis is also completely disabled.

The supported values for GREYLISTING are off, gross or postgrey. Gross is a more advanced greylisting server which blocks only hosts with a bad DNSBL reputation.

Currently, only a single RECIPIENT_DELIMITER is supported. Support for multiple delimiters will arrive with Dovecot v2.3.

FETCHMAIL_INTERVAL must be a number between 1 and 59 minutes.

### Files/Folders tree

/mnt/docker
└──mail
   ├──postfix
   │     custom.conf
   ├──postgrey
   │     postgrey.db
   │     ...
   ├──gross
   │     grossd.state
   ├──sieve
   │     default.sieve
   │     default.svbin
   ├──opendkim
   │  ├──domain.tld
   │  │     mail.private
   │  │     mail.txt
   ├──ssl
   │  ├──dhparams
   │  │     dh512.pem
   │  │     dh2048.pem
   │  ├──live (Let's Encrypt or other CA)
   │  │  ├──mail.domain.tld
   │  │  │     privkey.pem
   │  │  │     cert.pem
   │  │  │     chain.pem
   │  │  │     fullchain.pem
   │  ├──selfsigned (Auto-generated if no certificate found)
   │  │     cert.pem
   │  │     privkey.pem
   ├──vhosts
   │  ├──domain.tld
   │  │  ├──user
   │  │  │     .dovecot.sieve -> sieve/rainloop.user.sieve
   │  │  │     .dovecot.svbin
   │  │  │  ├──mail
   │  │  │  │  ├──.Archive
   │  │  │  │  ├──.Drafts
   │  │  │  │  ├──.Sent
   │  │  │  │  ├──.Spam
   │  │  │  │  ├──.Trash
   │  │  │  │  ├──cur
   │  │  │  │  ├──new
   │  │  │  │     ...
   │  │  │  ├──sieve
   │  │  │  │     rainloop.user.sieve (if using rainloop webmail)

Let's Encrypt certificate authority

To use Let's Encrypt certificates, setup your docker-compose.yml file like this :

mailserver:
  image: hardware/mailserver
  volumes:
    - /mnt/docker/nginx/certs:/etc/letsencrypt
    ...

nginx:
  image: wonderfall/boring-nginx
  volumes:
    - /mnt/docker/nginx/certs:/certs
    ...

Then generate Let's Encrypt certificates with xataz/letsencrypt, you can use other tools like lego if you want.

docker-compose stop nginx

docker run -it --rm \
  -v /mnt/docker/nginx/certs:/etc/letsencrypt \
  -p 80:80 -p 443:443 \
  xataz/letsencrypt \
    certonly --standalone \
    --rsa-key-size 4096 \
    --agree-tos \
    -m [email protected] \
    -d mail.domain.tld \ # <--- Mail FQDN is the first domain name, very important !
    -d webmail.domain.tld \
    -d postfixadmin.domain.tld

docker-compose up -d

• ⚠️ The common name of your ssl certifcate MUST be the same as your server's FQDN (for exemple, let's encrypt live subfolder name must be egual to domainname & hostname values of docker-compose file). Don't forget to add your FQDN in command above in first position.

• If you do not use let's encrypt, a default self-signed certificate (RSA 4096 bits SHA2) is generated here : /mnt/docker/mail/ssl/selfsigned/{cert.pem, privkey.pem}.

Another certificate authority (other than Let's Encrypt)

Put your certificates in /mnt/docker/nginx/certs/live/mail.domain.tld

⚠️ Required files in this folder :

• privkey.pem : Private key for the certificate
• cert.pem : Server certificate only
• chain.pem : Root and intermediate certificates only, excluding server certificate
• fullchain.pem : All certificates, including server certificate. This is concatenation of cert.pem and chain.pem

Then mount the volume like this :

mailserver:
  image: hardware/mailserver
  volumes:
    - /mnt/docker/nginx/certs:/etc/letsencrypt
    ...

Override postfix configuration

Postfix default configuration can be overrided providing a custom configuration file at postfix format. This can be used to also add configuration that are not in default configuration. Postfix documentation remains the best place to find configuration options.

Each line in the provided file will be loaded into Postfix. Create a new file here /mnt/docker/mail/postfix/custom.conf and add your custom options inside.

Example :

# /mnt/docker/mail/postfix/custom.conf

smtpd_banner = $myhostname ESMTP MyGreatMailServer
inet_protocols = ipv4
delay_notice_recipient = [email protected]
delay_warning_time = 2h

docker logs -f mailserver

[INFO] Override : smtpd_banner = $myhostname ESMTP MyGreatMailServer
[INFO] Override : inet_protocols = ipv4
[INFO] Override : delay_notice_recipient = [email protected]
[INFO] Override : delay_warning_time = 2h
[INFO] Custom Postfix configuration file loaded

Email client settings :

• IMAP/SMTP username : [email protected]
• Incoming IMAP server : mail.domain.tld (your FQDN)
• Outgoing SMTP server : mail.domain.tld (your FQDN)
• IMAP port : 993
• SMTP port : 587
• IMAP Encryption protocol : SSL/TLS
• SMTP Encryption protocol : STARTTLS

Components

• Postfix 2.11.3
• Dovecot 2.2.13
• OpenDKIM 2.9.2
• OpenDMARC 1.3.0
• Spamassassin 3.4.0
• Postgrey 1.35
• Fetchmail 6.3.26
• ClamAV 0.98.7
• Amavisd-new 2.10.1
• Amavisd-milter 1.5.0
• Supervisor 3.0r1
• Rsyslog 8.4.2
• ManageSieve server

Roadmap

• Use Rspamd instead of Spamassassin
• ClueGetter integration
• LDAP authentification (need contributors)

How to contribute

• Fork this repository
• Create a new feature branch for a new functionality or bugfix
• Code...
• Add integration tests in test/tests.bats
• Use make to build image locally and run tests
• Document your improvements
• Commit your changes
• Push your code and open a new pull request
• Use issues for any questions