Using Docker for a mail server

Question

I've been interested in docker for a while, but not jumped in yet. I have a need to set up a mail server, so thought maybe I could use this as a reason to learn more about docker. However, I'm unclear how to best go about it.

I've installed a mailserver on a VPS before, but not into multiple containers. I'd like to install Postfix, Dovecot, MySQL or Postgresql, and SpamAssassin, similar to what is described here:

https://www.digitalocean.com/community/tutorials/how-to-configure-a-mail-server-using-postfix-dovecot-mysql-and-spamassasin

However, what would be a good way to dockerize it? Would I simply put everything into a single container? Or would it be better to have MySQL in one container, Postfix in another, and additional containers for Dovecot and SpamAssassin? Or should some containers be shared?

Are there any HOWTOs on installing a mailserver using docker? If there is, I haven't found it yet.

Answer 1

The point of Docker isn't containerization for containerization's sake. It is to put together things that belong together and separate things that don't belong together.

With that in mind, the way I would set this up is with a container for the MySql database and another container for all of the mail components. The mail components are typically integrated with each other by calling each other's executables or by reading/writing shared files, so it does not make sense to separate them in separate containers anyway. Since the database could also be used for other things, and communication with it is done over a socket, it makes more sense for that to be a separate container.