Basic Installation

Setting up a Simple Mail-Server

This is a community contributed guide. Please let us know via a Github Issue if you're having any difficulty following the guide so that we can update it.

This guide is focused on only using SMTP ports (not POP3 and IMAP) with the intent to send received mail to another MTA service such as Gmail. It is not intended to have a MUA client (eg: Thunderbird) to retrieve mail directly from docker-mailserver via POP3/IMAP.

In this setup docker-mailserver is not intended to receive email externally, so no anti-spam or anti-virus software is needed, making the service lighter to run.

Open Relays

Adding the docker network's gateway to the list of trusted hosts (eg: using the network or connected-networks option), can create an open relay. For instance if IPv6 is enabled on the host machine, but not in Docker.

If you're running a version of docker-mailserver earlier than v10.2, you'll need to get setup.sh. Otherwise you can substitute ./setup.sh <command> with docker exec mailserver setup <command>.
Pull the docker image: docker pull docker.io/mailserver/docker-mailserver:latest.

Create the file docker-compose.yml with a content like this:

Example

version: '3.8'

services:
  mailserver:
    image: docker.io/mailserver/docker-mailserver:latest
    container_name: mailserver
    hostname: mail
    # Change this to your domain, it is used for your email accounts (eg: user@example.com):
    domainname: example.com
    ports:
      - "25:25"
      - "587:587"
      - "465:465"
    volumes:
      - ./docker-data/dms/mail-data/:/var/mail/
      - ./docker-data/dms/mail-state/:/var/mail-state/
      - ./docker-data/dms/mail-logs/:/var/log/mail/
      - ./docker-data/dms/config/:/tmp/docker-mailserver/
      # The "from" path will vary based on where your certs are locally:
      - ./docker-data/nginx-proxy/certs/:/etc/letsencrypt/
      - /etc/localtime:/etc/localtime:ro
    environment:
      - ENABLE_FAIL2BAN=1
      # Using letsencrypt for SSL/TLS certificates
      - SSL_TYPE=letsencrypt
      # Allow sending emails from other docker containers
      # Beware creating an Open Relay: https://docker-mailserver.github.io/docker-mailserver/edge/config/environment/#permit_docker
      - PERMIT_DOCKER=network
      # All env below are default settings:
      - ONE_DIR=1
      - ENABLE_POSTGREY=0
      - ENABLE_CLAMAV=0
      - ENABLE_SPAMASSASSIN=0
      # You may want to enable this: https://docker-mailserver.github.io/docker-mailserver/edge/config/environment/#spoof_protection
      # See step 8 below, which demonstrates setup with enabled/disabled SPOOF_PROTECTION:
      - SPOOF_PROTECTION=0
    cap_add:
      - NET_ADMIN # For Fail2Ban to work

The docs have a detailed page on Environment Variables for reference.

Firewalled ports

You may need to open ports 25, 587 and 465 on the firewall. For example, with the firewall ufw, run:

ufw allow 25
ufw allow 587
ufw allow 465

Configure your DNS service to use an MX record for the hostname (eg: mail) you configured in the previous step and add the SPF TXT record.

If you manually manage the DNS zone file for the domain, it would look something like this:
```
mail      IN  A   10.11.12.13

; mail-server for example.com
    3600  IN  MX  1  mail.example.com.

; Add SPF record
          IN TXT "v=spf1 mx ~all"
```
Then don't forget to change the serial number and to restart the service.

Generate DKIM keys for your domain via ./setup.sh config dkim.

Copy the content of the file docker-data/dms/config/opendkim/keys/example.com/mail.txt and add it to your DNS records as a TXT like SPF was handled above.

I use bind9 for managing my domains, so I just paste it on example.com.db:

mail._domainkey IN      TXT     ( "v=DKIM1; h=sha256; k=rsa; "
        "p=MIIBIjANBgkqhkiG9w0BAQEFACAQ8AMIIBCgKCAQEAaH5KuPYPSF3Ppkt466BDMAFGOA4mgqn4oPjZ5BbFlYA9l5jU3bgzRj3l6/Q1n5a9lQs5fNZ7A/HtY0aMvs3nGE4oi+LTejt1jblMhV/OfJyRCunQBIGp0s8G9kIUBzyKJpDayk2+KJSJt/lxL9Iiy0DE5hIv62ZPP6AaTdHBAsJosLFeAzuLFHQ6USyQRojefqFQtgYqWQ2JiZQ3"
        "iqq3bD/BVlwKRp5gH6TEYEmx8EBJUuDxrJhkWRUk2VDl1fqhVBy8A9O7Ah+85nMrlOHIFsTaYo9o6+cDJ6t1i6G1gu+bZD0d3/3bqGLPBQV9LyEL1Rona5V7TJBGg099NQkTz1IwIDAQAB" )  ; ----- DKIM key mail for example.com

Get an SSL certificate, we have a guide for you here (Let's Encrypt is a popular service to get free SSL certificates).
Start docker-mailserver and check the terminal output for any errors: docker-compose up.

Create email accounts and aliases:

With SPOOF_PROTECTION=0

./setup.sh email add admin@example.com passwd123
./setup.sh email add info@example.com passwd123
./setup.sh alias add admin@example.com external-account@gmail.com
./setup.sh alias add info@example.com external-account@gmail.com
./setup.sh email list
./setup.sh alias list

Aliases make sure that any email that comes to these accounts is forwarded to your third-party email address (external-account@gmail.com), where they are retrieved (eg: via third-party web or mobile app), instead of connecting directly to docker-mailserer with POP3 / IMAP.

With SPOOF_PROTECTION=1

./setup.sh email add admin.gmail@example.com passwd123
./setup.sh email add info.gmail@example.com passwd123
./setup.sh alias add admin@example.com admin.gmail@example.com
./setup.sh alias add info@example.com info.gmail@example.com
./setup.sh alias add admin.gmail@example.com external-account@gmail.com
./setup.sh alias add info.gmail@example.com external-account@gmail.com
./setup.sh email list
./setup.sh alias list

This extra step is required to avoid the 553 5.7.1 Sender address rejected: not owned by user error (the accounts used for submitting mail to Gmail are admin.gmail@example.com and info.gmail@example.com)

Send some test emails to these addresses and make other tests. Once everything is working well, stop the container with ctrl+c and start it again as a daemon: docker-compose up -d.