These tutorials are nice but you can just hack https://hub.docker.com/r/analogic/poste.io (shameless ad) or any other containerized solution. You will get fully working solution in couple minutes and it will be somewhat easy to keep mailserver updated...
This. I have been running my own mail server since UUCP bang paths and sendmail. I am slowly preparing to migrate to a containerized solution for exactly this reason. Managing the updates of all the parts going forward is just too heavy a load, while swapping in a new container is easy. The initial configuration is painful, just because there are so many options to decide on, but those decisions are all there anyway, whether you realize them on day one or not. I am planning to use this image[0].
