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Simple and full-featured mail server using Docker

alikhadivi/mailserver is a simple and full-featured mail server build as a set of multiple docker images, including:

  • Nginx : Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
  • Postfix : a full-set smtp email server
  • Dovecot : secure IMAP and POP3 email server
  • Rspamd : anti-spam filter with SPF, DKIM, DMARC, ARC, ratelimit and greylisting capabilities
  • Clamav : antivirus with automatic updates and third-party signature databases
  • Zeyple : automatic GPG encryption of all your emails
  • Sieve : email filtering (vacation auto-responder, auto-forward, etc...)
  • Fetchmail : fetch emails from external IMAP/POP3 server into local mailbox
  • Postfixadmin : web-based administration interface
  • Unbound: recursive caching DNS resolver with DNSSEC support
  • NSD : authoritative DNS server with DNSSEC support
  • SSL (With Certbot) : let's encrypt with auto-renewal (SAN and wildcard certificates), custom and self-signed certificates support
  • OpenLDAP : ldap support available
  • Supporting multiple virtual domains over MySQL/PostgreSQL backend

Summary

System Requirements

Please check, if your system meets the following minimum requirements :

With MariaDB/PostgreSQL and Redis on the same host

Type Without ClamAV With ClamAV
CPU 1 GHz 1 GHz
RAM 1.5 GiB 2 GiB

With MariaDB/PostgreSQL and Redis hosted on another server

Type Without ClamAV With ClamAV
CPU 1 GHz 1 GHz
RAM 512 MiB 1 GiB

Back to table of contents 🔼

Prerequisites

Cleaning

Please remove any web server and mail services running on your server. I recommend using a clean installation of your prefered distro. If you are using Ubuntu (or a Debian based OS), remember to remove the default MTA Exim4 :

# apt-get purge exim4*

Also make sure that no other application is interfering with mail server configuration :

# netstat -tulpn | grep -E -w '25|80|110|143|443|465|587|993|995|4190'

If this command returns any results please remove or stop the application running on that port.

Ports

If you have a firewall, unblock the following ports, according to your needs :

Service Software Protocol Port
HTTP Nginx TCP 80
HTTPS Nginx TCP 443
POP3 Dovecot TCP 110
POP3S Dovecot TCP 995
IMAP Dovecot TCP 143
IMAPS Dovecot TCP 993
ManageSieve Dovecot TCP 4190
SMTP Postfix TCP 25
SMTPS Postfix TCP 465
Submission Postfix TCP 587

DNS records and reverse PTR

A correct DNS setup is required, this step is very important.

HOSTNAME CLASS TYPE PRIORITY VALUE
mail IN A/AAAA any 1.2.3.4
spam IN CNAME any mail.domain.tld.
webmail IN CNAME any mail.domain.tld.
postfixadmin IN CNAME any mail.domain.tld.
@ IN MX 10 mail.domain.tld.
@ IN TXT any "v=spf1 a mx ip4:SERVER_IPV4 ~all"
mail._domainkey IN TXT any "v=DKIM1; k=rsa; p=YOUR DKIM Public Key"
_dmarc IN TXT any "v=DMARC1; p=reject; rua=mailto:postmaster@domain.tld; ruf=mailto:admin@domain.tld; fo=0; adkim=s; aspf=s; pct=100; rf=afrf; sp=reject"

Notes:

  • Make sure that the PTR record of your IP matches the FQDN (default : mail.domain.tld) of your mailserver host. This record is usually set in your web hosting interface.
  • DKIM, SPF and DMARC records are recommended to build a good reputation score.
  • The DKIM public key will be available on host after the container startup :
/opt/mail/dkim/domain.tld/public.key

To regenerate your public and private keys, remove the /opt/mail/dkim/domain.tld folder. By default a 1024-bit key is generated, you can increase this size by setting the OPENDKIM_KEY_LENGTH environment variable with a higher value. Check your domain registrar support to verify that it supports a TXT record long enough for a key larger than 1024 bits.

These DNS record will raise your trust reputation score and reduce abuse of your domain name. You can find more information here :

Testing

You can audit your mailserver with the following assessment services :

Back to table of contents 🔼

Installation

1 - Prepare your environment

Install Nginx and Certbot

sudo apt update
sudo apt install nginx
sudo snap install certbot --classic
# Create a new docker network for Traefik (IPv4 only)
docker network create http_network
# If you want to support IPv6, please refer to [IPv6 support]

# Create the required folders and files
mkdir -p /mnt/docker && cd /mnt/docker \
&& curl https://raw.githubusercontent.com/alikhadivi/mailserver/master/docker-compose.sample.yml -o docker-compose.yml \
&& curl https://raw.githubusercontent.com/alikhadivi/mailserver/master/sample.env -o .env \
&& curl https://raw.githubusercontent.com/alikhadivi/mailserver/master/ssl.sh -o ssl.sh \
&& curl https://raw.githubusercontent.com/alikhadivi/mailserver/master/gen-passwords.sh -o gen-passwords.sh \
&& chmod 600 docker-compose.yml .env \
&& chmod +x gen-passwords.sh ssl.sh \
&& ./gen-passwords.sh

Edit the .env, adapt to your needs, then create Nginx sites and get SSL:

./ssl.sh

start all services :

docker compose up -d

2 - Postfixadmin Config

1 - Go to the setup page : https://postfixadmin.domain.tld/setup.php

💡 Don't forget to add a new A/CNAME record in your DNS zone.

2 - Define the setup password

go to https://postfixadmin.domain.tld/setup.php and get hash of password then paste it to .env file like this:

POSTFIXADMIN_SETUP_PASSWORD='your_hash'

and run:

docker compose up -d

4 - Create your admin account

5 - Go to the login page : https://postfixadmin.your-domain.tld/

6 - You can now create your domains, mailboxes, alias...etc 😃

3 - Done, congratulation ! 🎉

At first launch, the container takes few minutes to generate SSL certificates (if needed), DKIM keypair and update clamav database, all of this takes some time (1/2 minutes).

List of webservices available:

Service URI
Rspamd dashboard https://spam.domain.tld/
Administration https://postfixadmin.domain.tld/
Webmail https://webmail.domain.tld/

You can check the startup logs with this command :

# docker logs -f mailserver

[INFO] Let's encrypt live directory found
[INFO] Using /etc/letsencrypt/live/mail.domain.tld folder
[INFO] Creating DKIM keys for domain domain.tld
[INFO] Database hostname found in /etc/hosts
[INFO] Fetchmail forwarding is enabled.
[INFO] Automatic GPG encryption is enabled.
[INFO] ManageSieve protocol is enabled.
[INFO] POP3 protocol is enabled.
-------------------------------------------------------------------------------------
2017-08-26T11:06:58.885562+00:00 mail root: s6-supervise : spawning clamd process
2017-08-26T11:06:59.059077+00:00 mail root: s6-supervise : spawning freshclam process
2017-08-26T11:06:59.395214+00:00 mail root: s6-supervise : spawning rspamd process
2017-08-26T11:07:01.615597+00:00 mail root: s6-supervise : spawning unbound process
2017-08-26T11:07:01.870856+00:00 mail root: s6-supervise : spawning postfix process
2017-08-26T11:07:03.303536+00:00 mail root: s6-supervise : spawning dovecot process
...

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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 1024
DEBUG_MODE Enable Postfix, Dovecot, Rspamd and Unbound verbose logging optional false
PASSWORD_SCHEME Passwords encryption scheme optional SHA512-CRYPT
DBDRIVER Database type: mysql, pgsql, ldap optional mysql
DBHOST Database instance ip/hostname optional mariadb
DBPORT Database instance port optional 3306 / 389 (sql/ldap)
DBUSER Database username optional postfix
DBNAME Database name optional postfix
DBPASS Database password or location of a file containing it required *1) null
REDIS_HOST Redis instance ip/hostname optional redis
REDIS_PORT Redis instance port optional 6379
REDIS_PASS Redis database password or location of a file containing it optional null
REDIS_NUMB Redis database number optional 0
RSPAMD_PASSWORD Rspamd WebUI and controller password or location of a file containing it required null
ADD_DOMAINS Add additional domains to the mailserver separated by commas (needed for dkim keys etc.) optional null
RELAY_NETWORKS Additional IPs or networks the mailserver relays without authentication optional null
WHITELIST_SPAM_ADDRESSES List of whitelisted email addresses separated by commas optional null
DISABLE_RSPAMD_MODULE List of disabled modules separated by commas optional null
DISABLE_CLAMAV Disable virus scanning optional false
DISABLE_SIEVE Disable ManageSieve protocol optional false
DISABLE_SIGNING Disable DKIM/ARC signing optional false
DISABLE_GREYLISTING Disable greylisting policy optional false
DISABLE_RATELIMITING Disable ratelimiting policy optional true
DISABLE_DNS_RESOLVER Disable the local DNS resolver optional false
DISABLE_SSL_WATCH Disable watching of acme.json and the Let's Encrypt directory optional false
ENABLE_POP3 Enable POP3 protocol optional false
ENABLE_FETCHMAIL Enable fetchmail forwarding optional false
ENABLE_ENCRYPTION Enable automatic GPG encryption optional false
FETCHMAIL_INTERVAL Fetchmail polling interval optional 10
RECIPIENT_DELIMITER RFC 5233 subaddress extension separator (single character only) optional +

*1) DBPASS is NOT required when using LDAP authentication

  • Use DEBUG_MODE to enable the debug mode. Switch to true to enable verbose logging for postfix, dovecot, rspamd and Unbound. To debug components separately, use this syntax : DEBUG_MODE=postfix,rspamd.
  • VMAIL_SUBDIR is the mail location subdirectory name /var/mail/vhosts/%domain/%user/$subdir. For more information, read this : https://wiki.dovecot.org/VirtualUsers/Home
  • PASSWORD_SCHEME for compatible schemes, read this : https://wiki.dovecot.org/Authentication/PasswordSchemes
  • 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.
  • Use DISABLE_DNS_RESOLVER if you have some DNS troubles and DNSSEC lookup issues with the local DNS resolver.
  • Use DISABLE_RSPAMD_MODULE to disable any module listed here : https://rspamd.com/doc/modules/

When using LDAP authentication the following additional variables become available. All DBUSER, DBNAME and DBPASS variables will not be used in this case:

Variable Description Type Default value
LDAP_TLS_ENABLED Enable TLS on LDAP optional false
LDAP_TLS_CA_FILE The TLS CA File required if LDAP_TLS_ENABLED
LDAP_TLS_FORCE Force TLS connections required if LDAP_TLS_ENABLED false
LDAP_BIND Bind to LDAP Server optional true
LDAP_BIND_DN The DN to bind to required if LDAP_BIND
LDAP_BIND_PW LDAP password or location of a file containing it required if LDAP_BIND
LDAP_DEFAULT_SEARCH_BASE The base DN for all lookus required
LDAP_DEFAULT_SEARCH_SCOPE The default scope for all lookups (sub, base or one) optional sub
LDAP_DOMAIN_SEARCH_BASE The search base for domain lookups optional ${LDAP_DEFAULT_SEARCH_BASE}
LDAP_DOMAIN_SEARCH_SCOPE The search scope for domain lookups optional ${LDAP_DEFAULT_SEARCH_SCOPE}
LDAP_DOMAIN_FILTER The search filter for domain lookups required
LDAP_DOMAIN_ATTRIBUTE The attibutes for domain lookup required
LDAP_DOMAIN_FORMAT The format for domain lookups optional
LDAP_MAILBOX_SEARCH_BASE The search base for mailbox lookups optional ${LDAP_DEFAULT_SEARCH_BASE}
LDAP_MAILBOX_SEARCH_SCOPE The search scope for mailbox lookups optional ${LDAP_DEFAULT_SEARCH_SCOPE}
LDAP_MAILBOX_FILTER The search filter for mailbox lookups required
LDAP_MAILBOX_ATTRIBUTE The attibutes for mailbox lookup required
LDAP_MAILBOX_FORMAT The format for domain mailbox optional
LDAP_ALIAS_SEARCH_BASE The search base for domain lookups optional ${LDAP_DEFAULT_SEARCH_BASE}
LDAP_ALIAS_SEARCH_SCOPE The search scope for domain lookups optional ${LDAP_DEFAULT_SEARCH_SCOPE}
LDAP_ALIAS_FILTER The search filter for domain lookups required
LDAP_ALIAS_ATTRIBUTE The attibutes for domain lookup required
LDAP_ALIAS_FORMAT The format for domain lookups optional
LDAP_FORWARD_SEARCH_BASE The search base for forward lookups optional ${LDAP_DEFAULT_SEARCH_BASE}
LDAP_FORWARD_SEARCH_SCOPE The search scope for forward lookups optional ${LDAP_DEFAULT_SEARCH_SCOPE}
LDAP_FORWARD_FILTER The search filter for forward lookups optional
LDAP_FORWARD_ATTRIBUTE The attibutes for forward lookup optional
LDAP_FORWARD_FORMAT The format for forward lookups optional
LDAP_GROUP_SEARCH_BASE The search base for group lookups optional ${LDAP_DEFAULT_SEARCH_BASE}
LDAP_GROUP_SEARCH_SCOPE The search scope for group lookups optional ${LDAP_DEFAULT_SEARCH_SCOPE}
LDAP_GROUP_FILTER The search filter for group lookups optional
LDAP_GROUP_ATTRIBUTE The attibutes for group lookup optional
LDAP_GROUP_FORMAT The format for group lookups optional
LDAP_SENDER_SEARCH_BASE The search base for sender lookups optional ${LDAP_DEFAULT_SEARCH_BASE}
LDAP_SENDER_SEARCH_SCOPE The search scope for sender lookups optional ${LDAP_DEFAULT_SEARCH_SCOPE}
LDAP_SENDER_FILTER The search filter for sender lookups required
LDAP_SENDER_ATTRIBUTE The attibutes for sender lookup required
LDAP_SENDER_FORMAT The format for sender lookups required
LDAP_DOVECOT_USER_ATTRS Dovecot user attribute mapping required
LDAP_DOVECOT_USER_FILTER Dovecot user search filter required
LDAP_DOVECOT_PASS_ATTRS Dovecot user password attribute mapping required
LDAP_DOVECOT_PASS_FILTER Dovecot user password filter required
LDAP_DOVECOT_ITERATE_ATTRS Dovecot user iterate attributes optional
LDAP_DOVECOT_ITERATE_FILTER Dovecot user iterate filters optional
LDAP_MASTER_USER_ENABLED Enable LDAP master users optional false
LDAP_MASTER_USER_SEPARATOR LDAP master user seperator required if LDAP_MASTER_USER_ENABLED *
LDAP_MASTER_USER_SEARCH_BASE LDAP master user search base required if LDAP_MASTER_USER_ENABLED ${LDAP_DEFAULT_SEARCH_BASE}
LDAP_MASTER_USER_SEARCH_SCOPE LDAP master user scope required if LDAP_MASTER_USER_ENABLED ${LDAP_DEFAULT_SEARCH_SCOPE}
LDAP_DOVECOT_MASTER_USER_ATTRS LDAP master user dovecot attributes required if LDAP_MASTER_USER_ENABLED
LDAP_DOVECOT_MASTER_USER_FILTER LDAP master user dovecot search filter required if LDAP_MASTER_USER_ENABLED

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Automatic GPG encryption of all your emails

How does it work ?

Zeyple catches email from the postfix queue, then encrypts it if a corresponding recipient's GPG public key is found. Finally, it puts it back into the queue.

zeyple

Enable automatic GPG encryption

❗ Please enable this option carefully and only if you know what you are doing.

Switch ENABLE_ENCRYPTION environment variable to true. The public keyring will be saved in /var/mail/zeyple/keys. Please don't change the default value of RECIPIENT_DELIMITER (default = "+"). If encryption is enabled with another delimiter, Zeyple could have an unpredictable behavior.

Import your public key

⚠️ Make sure to send your public key on a gpg keyserver before to run the following command.

docker exec -ti mailserver encryption.sh import-key YOUR_KEY_ID

Import all recipients public keys

This command browses all /var/mail/vhosts/* domains directories and users subdirectories to find all the recipients addresses in the mailserver.

docker exec -ti mailserver encryption.sh import-all-keys

Specify another gpg keyserver

docker exec -ti mailserver encryption.sh import-key YOUR_KEY_ID hkp://pgp.mit.edu
docker exec -ti mailserver encryption.sh import-all-keys hkp://keys.gnupg.net

Run other GPG options

You can use all options of gpg command line except an already assigned parameter called --homedir.

docker exec -ti mailserver encryption.sh --list-keys
docker exec -ti mailserver encryption.sh --fingerprint
docker exec -ti mailserver encryption.sh --refresh-keys
docker exec -ti mailserver encryption.sh ...

Documentation : https://www.gnupg.org/documentation/manuals/gnupg/Operational-GPG-Commands.html

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Relaying from other networks

The RELAY_NETWORKS is a space separated list of additional IP addresses and subnets (in CIDR notation) which the mailserver relays without authentication. Hostnames are possible, but generally disadvised. IPv6 addresses must be surrounded by square brackets. You can also specify an absolut path to a file with IPs and networks so you can keep it on a mounted volume. Note that the file is not monitored for changes.

You can use this variable to allow other local containers to relay via the mailserver. Typically you would set this to the IP range of the default docker bridge (172.17.0.0/16) or the default network of your compose. If you are unable to determine, you might just add all RFC 1918 addresses 192.168.0.0/16 172.16.0.0/12 10.0.0.0/8

⚠️ A value like 0.0.0.0/0 will turn your mailserver into an open relay!

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MTA-STS

MTA-STS is a new standard that makes it possible to send downgrade-resistant email over SMTP. In that sense, it is like an alternative to DANE but it does this by piggybacking on the browser Certificate Authority model, not DNSSEC.

To enable Strict Transport Security on your mailserver configure the following things :

  1. Add a TLSRPT DNS TXT record at _smtp._tls on your domain, e.g. _smtp._tls.domain.tld, with something like v=TLSRPTv1; rua=mailto:postmaster@domain.tld.
  2. Add a MTA-STS DNS TXT record at _mta-sts on your domain, e.g. _mta-sts.domain.tld, with something like v=STSv1; id=2018072801.
  3. Add a subdomain mta-sts to your domain (note the lack of an underscore) and serve a policy file on https://mta-sts.domain.tld/.well-known/mta-sts.txt.

Here is an example policy file:

version: STSv1
mode: enforce
max_age: 10368000
mx: mail.domain.tld

Test your mail domain using a MTA-STS validator like Hardenize. You can also add your domain name in the STARTTLS Policy List maintained by EFF.

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Third-party clamav signature databases

Clamav-unofficial-sigs provides a simple way to download and update third-party signature databases provided by Sanesecurity, FOXHOLE, OITC, Scamnailer, BOFHLAND, CRDF, Porcupine, Securiteinfo, MalwarePatrol, Yara-Rules Project, etc.

Readme : https://github.com/extremeshok/clamav-unofficial-sigs

Required Ports

Software Protocol Port
Rsync TCP 873
Curl TCP 443

Enable clamav-unofficial-sigs

Create your user.conf file under /opt/mail/clamav-unofficial-sigs directory to configure clamav-unofficial-sigs updater. This file override the default configuration specified in os.conf and master.conf. Don't forget, once you have completed the configuration of this file, set the value of user_configuration_complete to yes otherwise the script will not be able to execute. As Yara rules are broken with clamav ≥ 0.100, we disable Yara rules for now.

# /opt/mail/clamav-unofficial-sigs/user.conf

# =========================
# MalwarePatrol : https://www.malwarepatrol.net
# MalwarePatrol 2016 (free) clamav signatures
#
# 1. Sign up for an account : https://www.malwarepatrol.net/signup-free.shtml
# 2. You will receive an email containing your password/receipt number
# 3. Login to your account at malwarePatrol
# 4. In My Accountpage, choose the ClamAV list you will download. Free subscribers only get ClamAV Basic, commercial subscribers have access to ClamAV Extended. Do not use the agressive lists.
# 5. In the download URL, you will see 3 parameters: receipt, product and list, enter them in the variables below.
# malwarepatrol_receipt_code="YOUR-RECEIPT-NUMBER"
# malwarepatrol_product_code="8"
# malwarepatrol_list="clamav_basic"
# malwarepatrol_free="yes"

# =========================
# SecuriteInfo : https://www.SecuriteInfo.com
# SecuriteInfo 2015 free clamav signatures
#
# Usage of SecuriteInfo 2015 free clamav signatures : https://www.securiteinfo.com
# - 1. Sign up for a free account : https://www.securiteinfo.com/clients/customers/signup
# - 2. You will receive an email to activate your account and then a followup email with your login name
# - 3. Login and navigate to your customer account : https://www.securiteinfo.com/clients/customers/account
# - 4. Click on the Setup tab
# - 5. You will need to get your unique identifier from one of the download links, they are individual for every user
# - 5.1. The 128 character string is after the http://www.securiteinfo.com/get/signatures/
# - 5.2. Example https://www.securiteinfo.com/get/signatures/your_unique_and_very_long_random_string_of_characters/securiteinfo.hdb
#   Your 128 character authorisation signature would be : your_unique_and_very_long_random_string_of_characters
# - 6. Enter the authorisation signature into the config securiteinfo_authorisation_signature: replacing YOUR-SIGNATURE-NUMBER with your authorisation signature from the link
# securiteinfo_authorisation_signature="YOUR-SIGNATURE-NUMBER"

# We disable Yara rules for now because they are broken with clamav releases > 0.100
yararulesproject_enabled="no"
enable_yararules="no"

# After you have completed the configuration of this file, set the value to "yes"
user_configuration_complete="yes"

If the startup script detects this file, clamav-unofficial-sigs is automatically enabled and third-party databases downloaded under /opt/mail/clamav after clamav startup. Once the databases are downloaded, a SIGUSR2 signal is sent to clamav to reload the signature databases :

docker logs -f mailserver

[INFO] clamav-unofficial-sigs is enabled (user configuration found)
[...]
s6-supervise : clamav unofficial signature update running
s6-supervise : virus database downloaded, spawning clamd process
[...]
s6-supervise : clamav unofficial signature update done
clamd[xxxxxx]: Reading databases from /var/lib/clamav
clamd[xxxxxx]: Database correctly reloaded (6812263 signatures)

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Unbound DNS resolver

Unbound is a validating, recursive, and caching DNS resolver inside the container, you can control it with the remote server control utility.

Some examples :

# Display server status
docker exec -ti mailserver unbound-control status

# Print server statistics
docker exec -ti mailserver unbound-control stats_noreset

# Reload the server. This flushes the cache and reads the config file.
docker exec -ti mailserver unbound-control reload

Documentation : https://www.unbound.net/documentation/unbound-control.html

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LDAP support

This mailserver supports LDAP now aswell. Please keep in mind that LDAP itself is an already complicated system and using this mailserver with LDAP will require you to already have a deeper understanding on how LDAP, postfix and dovecot works. Due to the nature of LDAP there is no "default" setup you can or is suggested to be used. This means a lot of configuration is required to set this mailserver up with your LDAP system and it will definetly not work out of the box.

To enable LDAP you have to set DBDRIVER to ldap. DBHOST and DBPORT must point to the LDAP server used. DBUSER, DBNAME, DBPASS enviroment variables will not be used in this case.

If you want to use TLS set LDAP_TLS_ENABLED to true and specify a LDAP_TLS_CA_FILE. If you want to require the use of TLS set LDAP_TLS_FORCE to true.

If you want to bind to the LDAP server (default) set LDAP_BIND to true (default) and give your bind user dn (full path) as LDAP_BIND_DN and password as LDAP_BIND_PW. If a path to a existing file is given in LDAP_BIND_PW the content of the file will be used instead.

All lookups will by default use LDAP_DEFAULT_SEARCH_BASE as base and LDAP_DEFAULT_SEARCH_SCOPE as scope. But for any query a specific base and scope can be provided aswell. Valid scopes are: sub for subtree meaning all nodes below the base. one for all direct child nodes of the base and one for only the base node itself.

Unlike with postfixadmin where all tables are fixed, this mailserver is intended to work with existing ldap structures. This requires all lookups to be specified by you.

There are 4 required and 2 optional lookups for postfix that have to be provided by you. Each consists of 5 variables. The loopups are: Domain, Mailbox, Alias and Sender (all 4 required) and Forward and Group (optional). Each has the enviroment variables LDAP_XXX_SEARCH_BASE, LDAP_XXX_SEARCH_SCOPE, LDAP_XXX_FILTER, LDAP_XXX_ATTRIBUTE and LDAP_XXXN_FORMAT (optional) where XXX* must be replaced with DOMAIN, MAILBOX, ALIAS, SENDER, FORWARD or GROUP. E.g. LDAP_DOMAIN_SEARCH_BASE or LDAP_MAILBOX_FILTER

The LDAP_XXX_SEARCH_BASE is the search base dn. It will default to LDAP_DEFAULT_SEARCH_BASE as LDAP_XXX_SEARCH_SCOPE will default to LDAP_DEFAULT_SEARCH_SCOPE (which defaults to sub).

The LDAP_XXX_FILTER must be a valid LDAP query filter. For a documentation of LDAP query filters you can look at https://ldap.com/ldap-filters/. For a list of valid replacement tokens please look at http://www.postfix.org/ldap_table.5.html in the section query_filter. Some examples:

LDAP_DOMAIN_FILTER="(&(mail=*@%s)(objectClass=mailAccount))"

LDAP_MAILBOX_FILTER="(&(mail=%s)(objectClass=mailAccount))"

LDAP_SENDER_FILTER="(&(|(mail=%s)(mailalias=%s))(objectClass=mailAccount))"

The LDAP_XXX_ATTRIBUTE specifies which attribute of the found LDAP objects will be used. Usually these are either mail, uid, mailalias or mailacceptinggeneralid but may be completly different ones depending on your LDAP setup.

LDAP_XXX_FORMAT can be used to reformat the result. E.g. you can use LDAP_MAILBOX_FORMAT="/var/mail/vhosts/%d/%s/mail/" to set a fixed path for the mailbox location if the path is not stored within LDAP.

The optional FORWARD and GROUP lookups are technically identical to the ALIAS lookup and could be used interchangeably but are intended for additional alias/group/forward lookups. So you can use aliases using an alias field in your user objects. Forwards as source and destination mapping fields in forwarding objects and group address and group member emails in group objects. But you can also use them in different ways to suit your system.

Then you also have to provide the lookups for dovecot. These will probably be similar to your postfix lookups but may and will differ in some cases. The variables neccessary are LDAP_DOVECOT_USER_ATTRS, LDAP_DOVECOT_USER_FILTER, LDAP_DOVECOT_PASS_ATTRS, LDAP_DOVECOT_PASS_FILTER, LDAP_DOVECOT_ITERATE_ATTRS, LDAP_DOVECOT_ITERATE_FILTER. They correspond directly to the dovecot variables of the same name. While the user and pass attributes and filters are required, the iterate attributes and filters are not. For more detailed information please look at https://wiki.dovecot.org/AuthDatabase/LDAP/Userdb. Note that multiple attribures may be required per query and must be provided in a different form than for postfix! Here are some examples:

LDAP_DOVECOT_USER_ATTRS="=home=/var/mail/vhosts/%d/%n/,=mail=maildir:/var/mail/vhosts/%d/%n/mail/,mailuserquota=quota=quota_rule=*:bytes=%\$$"
LDAP_DOVECOT_USER_FILTER="(&(mail=%u)(objectClass=mailAccount))"
LDAP_DOVECOT_PASS_ATTRS="mail=user,userPassword=password"
LDAP_DOVECOT_PASS_FILTER="(&(mail=%u)(objectClass=mailAccount))"
LDAP_DOVECOT_ITERATE_ATTRS="mail=user"
LDAP_DOVECOT_ITERATE_FILTER="(objectClass=mailAccount)"

This mailserver also supports the user of master users that are allowed to log into other users mailboxes using their own password. This can be used e.g. for shared mailboxes or external imap services that should be able to connect to all inboxes via imap while not knowing the users passwords. To enable the use of master users set LDAP_MASTER_USER_ENABLED to true. With LDAP_MASTER_USER_SEPARATOR the separator can be specified (default is *). So you can log in with the username normaluser@yoursystem.com*masteruser@yoursystem.com or normaluser*masteruser if you only use usernames as logins. The password then has to be the password of the master user. LDAP_MASTER_USER_SEARCH_BASE, LDAP_MASTER_USER_SEARCH_SCOPE, LDAP_DOVECOT_MASTER_USER_ATTRS and LDAP_DOVECOT_MASTER_USER_FILTER work analogous to the dovecot user lookups. For more detailed documentation please look at https://wiki.dovecot.org/Authentication/MasterUsers . Note that %u is the master user name in this case and %{login_user} can be used to get the user name of the user to be loged in.

LDAP_MASTER_USER_ENABLED=true
LDAP_DOVECOT_MASTER_PASS_ATTRS="mail=user,userPassword=password"
LDAP_DOVECOT_MASTER_PASS_FILTER="(&(mail=%u)(st=%{login_user})(objectClass=mailAccount))"

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IPv6 support

If you want to support inbound IPv6 connections, you need to create a docker network with IPv6 enabled, otherwise, you may have some issues with docker internal networking.

The procedure is quite simple:

  • Remove your old http_network (if you already have created it)
docker network rm http_network

  • Choose a private ipv6 address range (/64)

  • Create a docker network with IPv6 enabled

# Replace subnet mask with your own "Combined/CID"
docker network create http_network --ipv6 --subnet "fd00:0000:0000:0000::/64"
  • Append this to your docker-compose.yml
# IPv6NAT
# https://github.com/robbertkl/docker-ipv6nat
# https://hub.docker.com/r/robbertkl/ipv6nat/
ipv6nat:
  image: robbertkl/ipv6nat
  container_name: ipv6nat
  restart: ${RESTART_MODE}
  volumes:
    - /var/run/docker.sock:/var/run/docker.sock:ro
    - /lib/modules:/lib/modules:ro
  depends_on:
    - mailserver
  cap_add:
    - NET_ADMIN
    - SYS_MODULE
  network_mode: "host"
  • Create a record named mail of type AAAA with your public IPv6 address in your DNS provider.

Done! This is all the configuration needed to enable inbound IPv6 support on this mailserver.

You can read more on how and why robbertkl/docker-ipv6nat container mimics NAT for IPv6 on his page.

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Persistent files and folders in /opt/mail Docker volume

/mnt/docker
└──mail
   ├──postfix
   |     custom.conf
   |     sender_access
   |  ├──spool (Postfix queues directory)
   │  │     defer
   │  │     flush
   │  │     hold
   │  │     maildrop
   │  │     ...
   ├──dovecot
   |     instances
   |     ssl-parameters.dat
   |  ├──conf.d (Custom dovecot configuration)
   ├──clamav (ClamAV databases directory)
   │     bytecode.cvd
   │     daily.cld
   │     main.cvd
   ├──clamav-unofficial-sigs
   │     user.conf
   ├──rspamd (Rspamd databases directory)
   │     rspamd.rrd
   |     stats.ucl
   ├──zeyple
   │  ├──keys (GPG public keyring)
   │  │     pubring.kbx
   │  │     trustdb.gpg
   │  │     ...
   ├──sieve
   │     default.sieve
   │     custom.sieve (custom default sieve rules for all users)
   ├──dkim
   │  ├──domain.tld
   │  │     private.key
   │  │     public.key
   ├──ssl
   │  ├──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)

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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 /opt/mail/postfix/custom.conf and add your custom options inside.

To edit services in master.cf configuration file, SFP prefixes are available to indicate what you want to change.

  • S| = service entry (service/type=value)
  • F| = service field (service/type/field=value)
  • P| = service parameter (service/type/parameter=value)

Example :

# /opt/mail/postfix/custom.conf

# main.cf parameters
smtpd_banner = $myhostname ESMTP MyGreatMailServer
inet_protocols = ipv4
delay_notice_recipient = admin@domain.tld
delay_warning_time = 2h

# master.cf services
S|submission/inet=submission inet n       -       -       -       -       smtpd
P|submission/inet/syslog_name=postfix/submission-custom
P|submission/inet/smtpd_tls_security_level=may
P|submission/inet/smtpd_tls_ciphers=medium
F|smtp/unix/chroot=n
docker logs -f mailserver

[INFO] Override parameter in main.cf : smtpd_banner = $myhostname ESMTP MyGreatMailServer
[INFO] Override parameter in main.cf : inet_protocols = ipv4
[INFO] Override parameter in main.cf : delay_notice_recipient = admin@domain.tld
[INFO] Override parameter in main.cf : delay_warning_time = 2h
[INFO] Override service entry in master.cf : submission/inet=submission inet n       -       -       -       -       smtpd
[INFO] Override service parameter in master.cf : submission/inet/syslog_name=postfix/submission-custom
[INFO] Override service parameter in master.cf : submission/inet/smtpd_tls_security_level=may
[INFO] Override service parameter in master.cf : submission/inet/smtpd_tls_ciphers=medium
[INFO] Override service field in master.cf : smtp/unix/chroot=n
[INFO] Custom Postfix configuration file loaded

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Custom configuration for dovecot

Sometimes you might want to add additional configuration parameters or override the default ones. You can do so by placing configuration files to the persistent folder /opt/mail/dovecot/conf.d.

Example:

# /opt/mail/dovecot/conf.d/20-imap.conf

protocol imap {

  mail_max_userip_connections = 100

}

# /opt/mail/dovecot/conf.d/90-quota.conf

plugin {

  quota_rule2 = Trash:storage=+200M
  quota_exceeded_message = You have exceeded your mailbox quota.

}

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Postfix blacklist

To block some senders or an entire domain, create a new file named sender_access in /opt/mail/postfix.

# /opt/mail/postfix/sender_access
# Format : <address|domain> <action>

domain.tld REJECT
spam@domain2.tld REJECT
docker logs -f mailserver

NOQUEUE: reject: 554 5.7.1 <john.doe@domain.tld>: Sender address rejected: Access denied

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Email client settings

  • IMAP/SMTP username : user@domain.tld
  • 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

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Components

  • Postfix
  • Dovecot
  • Rspamd
  • Fetchmail
  • ClamAV
  • Clamav Unofficial
  • Zeyple
  • Unbound
  • s6
  • Rsyslog
  • ManageSieve server

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