Docker compose requirements

Hardware considerations

You should make sure that your hardware (virtual or physical) is compatible with the latest Linux kernel. Also, you should have at least 2GB of total memory and 1GB of free memory when running Mailu.

Pick a distribution

The mail server runs as a set of Docker containers. It is thus almost agnostic of the underlying operating system as long as a fairly recent Linux kernel is running and the Docker API (>= 1.11) is available.

Because most of our tests run on Debian Jessie and Debian Stretch, 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 Stretch. The differences with other system will hardly be noticeable however.

Install the distribution

First, install Debian Stretch 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) ans 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 configured (see /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 25, 80, 110, 143, 443, 465, 587, 993 or 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 should use 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.

Install Docker

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 by following the instructions from the Docker website if you plan on using the CompComposesoe flavor. Compose is a management tool for Docker, especially suited for multiple containers systems like Mailu.

Once everything is setup, you should be able to run the following commands (exact version numbers do not matter):

$ docker version
Client:
 Version:      1.11.2
 API version:  1.23
 Go version:   go1.6.2
 Git commit:   b9f10c9
 Built:        Sun Jun  5 23:17:55 2016
 OS/Arch:      linux/amd64

Server:
 Version:      1.11.1
 API version:  1.23
 Go version:   go1.6.2
 Git commit:   5604cbe
 Built:        Mon May  2 00:06:51 2016
 OS/Arch:      linux/amd64

$ docker-compose version
docker-compose version 1.7.1, build 6c29830
docker-py version: 1.8.1
CPython version: 3.5.1
OpenSSL version: OpenSSL 1.0.2h  3 May 2016