Docker compose requirements
You should make sure that your hardware (virtual or physical) is compatible with the latest Linux kernel. The minimal required memory and swap are:
When using antivirus (clamav):
3GB of memory
1GB of swap
When not using antivirus (clamav):
1GB of memory
1GB of swap
Pick a distribution
The mail server runs as a set of Docker containers, so it is almost operating system agnostic.
Because most of our tests run on Debian stable, we recommend one of these for the base system. Mailu should however be able to run on any of the officially supported distributions.
For the purpose of this guide, all examples are based on Debian stable. The differences with other system will however hardly be noticeable.
Install the distribution
First, install Debian stable from the netinstall CD image. When installing, make sure that you either:
setup a root ext4 partition,
or setup a root btrfs partition,
or leave enough unpartitionned space for a dedicated ext4 or btrfs partition.
If you chose to create a dedicated partition, simply mount it to
/var/lib/docker. You could also create a separate partition (ext4 is a
sane default) and mount it to
/mailu for storing e-mail data.
Docker supports AUFS over ext4 and btrfs as stable storage drivers. Other filesystems are supported such as OverlayFS. If you know what you are doing, you should go for it.
Mailu uses Docker port forwarding from the host to make services
available to external users. First, your host should have a public IP address
/etc/network/interfaces) or your router should
forward connections to its internal IP address. Due to spam problems and
reputation services, it is highly recommended that you use a dedicated IP
address for your mail server and that you have a dedicated hostname
with forward and reverse DNS entries for this IP address.
Also, your host must not listen on ports
995 as these are used by Mailu
services. Therefore, you should disable or uninstall any program that is
listening on these ports (or have them listen on a different port). For
instance, on a default Debian install:
apt-get autoremove --purge exim4 exim4-base
Finally, Docker relies heavily on
iptables for port forwardings. You
iptables-persistent (or any equivalent tool on other
systems) for managing persistent rules. If you were brave enough to switch to
nftables, you will have to rollback until official support is released
by Docker or setup your own rulesets.
Mailu relies on some of the latest Docker features. Therefore, you should install Docker from the official repositories instead of your distribution ones.
The Docker website is full of detailed instructions about setting up a proper Docker install. Default configuration should be suited for Mailu.
Additionally, you must install
docker compose v2 by following the instructions
from the Docker website if you plan on using the Compose flavor. Compose is a
management tool for Docker, especially suited for multiple containers systems
Once everything is setup, you should be able to run the following commands (exact version numbers do not matter):
$ docker version Client: Docker Engine - Community Version: 20.10.22 API version: 1.41 Go version: go1.18.9 Git commit: 3a2c30b Built: Thu Dec 15 22:27:03 2022 OS/Arch: linux/arm64 Context: default Experimental: true Server: Docker Engine - Community Engine: Version: 20.10.22 API version: 1.41 (minimum version 1.12) Go version: go1.18.9 Git commit: 42c8b31 Built: Thu Dec 15 22:25:25 2022 OS/Arch: linux/arm64 Experimental: false containerd: Version: 1.6.14 GitCommit: 9ba4b250366a5ddde94bb7c9d1def331423aa323 runc: Version: 1.1.4 GitCommit: v1.1.4-0-g5fd4c4d docker-init: Version: 0.19.0 GitCommit: de40ad0 $ docker compose version Docker Compose version v2.14.1