docker-mailserver/docs/content/usage.md

title
Usage

This pages explains how to get started with DMS. The guide uses Docker Compose as a reference. In our examples, a volume mounts the host location docker-data/dms/config/ to /tmp/docker-mailserver/ inside the container.

Preliminary Steps

Before you can get started with deploying your own mail server, there are some requirements to be met:

1. You need to have a host that you can manage.
2. You need to own a domain, and you need to able to manage DNS for this domain.

Host Setup

There are a few requirements for a suitable host system:

1. The host should have a static IP address; otherwise you will need to dynamically update DNS (undesirable due to DNS caching)
2. The host should be able to send/receive on the necessary ports for mail
3. You should be able to set a PTR record for your host; security-hardened mail servers might otherwise reject your mail server as the IP address of your host does not resolve correctly/at all to the DNS name of your server.

!!! note "About the Container Runtime"

On the host, you need to have a suitable container runtime (like _Docker_ or _Podman_) installed. We assume [_Docker Compose_][docker-compose] is [installed][docker-compose-installation]. We have aligned file names and configuration conventions with the latest [Docker Compose (currently V2) specification][docker-compose-specification].

If you're using podman, make sure to read the related [documentation][docs-podman].

Minimal DNS Setup

The DNS setup is a big and essential part of the whole setup. There is a lot of confusion for newcomers and people starting out when setting up DNS. This section provides an example configuration and supplementary explanation. We expect you to be at least a bit familiar with DNS, what it does and what the individual record types are.

Now let's say you just bought example.com and you want to be able to send and receive e-mails for the address test@example.com. On the most basic level, you will need to

1. set an MX record for your domain example.com - in our example, the MX record contains mail.example.com
2. set an A record that resolves the name of your mail server - in our example, the A record contains 11.22.33.44
3. (in a best-case scenario) set a PTR record that resolves the IP of your mail server - in our example, the PTR contains mail.example.com

We will later dig into DKIM, DMARC & SPF, but for now, these are the records that suffice in getting you up and running. Here is a short explanation of what the records do:

• The MX record tells everyone which (DNS) name is responsible for e-mails on your domain. Because you want to keep the option of running another service on the domain name itself, you run your mail server on mail.example.com. This does not imply your e-mails will look like test@mail.example.com, the DNS name of your mail server is decoupled of the domain it serves e-mails for. In theory, you mail server could even serve e-mails for test@some-other-domain.com, if the MX record for some-other-domain.com points to mail.example.com.
• The A record tells everyone which IP address the DNS name mail.example.com resolves to.
• The PTR record is the counterpart of the A record, telling everyone what name the IP address 11.22.33.44 resolves to.

If you setup everything, it should roughly look like this:

$ dig @1.1.1.1 +short MX example.com
mail.example.com
$ dig @1.1.1.1 +short A mail.example.com
11.22.33.44
$ dig @1.1.1.1 +short -x 11.22.33.44
mail.example.com

Deploying the Actual Image

Tagging Convention

To understand which tags you should use, read this section carefully. Our CI will automatically build, test and push new images to the following container registries:

1. DockerHub (docker.io/mailserver/docker-mailserver)
2. GitHub Container Registry (ghcr.io/docker-mailserver/docker-mailserver)

All workflows are using the tagging convention listed below. It is subsequently applied to all images.

Event	Image Tags
push on master	edge
push a tag (v1.2.3)	1.2.3, 1.2, 1, latest

Get All Files

Issue the following commands to acquire the necessary files:

DMS_GITHUB_URL="https://raw.githubusercontent.com/docker-mailserver/docker-mailserver/master"
wget "${DMS_GITHUB_URL}/compose.yaml"
wget "${DMS_GITHUB_URL}/mailserver.env"

Configuration Steps

1. First edit compose.yaml to your liking
   • Substitute mail.example.com according to your FQDN.
   • If you want to use SELinux for the ./docker-data/dms/config/:/tmp/docker-mailserver/ mount, append -z or -Z.
2. Then configure the environment specific to the mail server by editing mailserver.env, but keep in mind that:
   • only basic VAR=VAL is supported
   • do not quote your values
   • variable substitution is not supported, e.g. OVERRIDE_HOSTNAME=$HOSTNAME.$DOMAINNAME does not work

Get Up and Running

!!! danger "Using the Correct Commands For Stopping and Starting DMS"

**Use `docker compose up / down`, not `docker compose start / stop`**. Otherwise, the container is not properly destroyed and you may experience problems during startup because of inconsistent state.

Using `Ctrl+C` **is not supported either**!

For an overview of commands to manage DMS config, run: docker exec -it <CONTAINER NAME> setup help.

??? info "Usage of setup.sh when no DMS Container Is Running"

We encourage you to directly use `setup` inside the container (like shown above). If you still want to use `setup.sh`, here's some information about it.

If no DMS container is running, any `./setup.sh` command will check online for the `:latest` image tag (the current _stable_ release), performing a `docker pull ...` if necessary followed by running the command in a temporary container:

```console
$ ./setup.sh help
Image 'ghcr.io/docker-mailserver/docker-mailserver:latest' not found. Pulling ...
SETUP(1)

NAME
    setup - 'docker-mailserver' Administration & Configuration script
...

$ docker run --rm ghcr.io/docker-mailserver/docker-mailserver:latest setup help
SETUP(1)

NAME
    setup - 'docker-mailserver' Administration & Configuration script
...
```

On first start, you will need to add at least one email account (unless you're using LDAP). You have two minutes to do so, otherwise DMS will shutdown and restart. You can add accounts by running docker exec -ti <CONTAINER NAME> setup email add user@example.com. That's it! It really is that easy.

Further Miscellaneous Steps

Setting up TLS

You definitely want to setup TLS. Please refer to our documentation about TLS.

Aliases

You should add at least one alias, the postmaster alias. This is a common convention, but not strictly required.

docker exec -ti <CONTAINER NAME> setup alias add postmaster@example.com user@example.com

Advanced DNS Setup - DKIM, DMARC & SPF

You will very likely want to configure your DNS with these TXT records: SPF, DKIM, and DMARC. We also ship a dedicated page in our documentation about the setup of DKIM, DMARC & SPF.

Custom User Changes & Patches

If you'd like to change, patch or alter files or behavior of DMS, you can use a script. See this part of our documentation for a detailed explanation.

Testing

Here are some tools you can use to verify your configuration:

1. MX Toolbox
2. DMARC Analyzer
3. mail-tester.com
4. multiRBL.valli.org