Add documentation for outgoing ports and destinations

[Stefomat]

Hi,

In the installation requirements there is a chapter that deals with firewalls and ports. It explains exactly which incoming ports Mailcow needs and how to check if they are free. However, outgoing ports are not covered in this chapter. Outgoing ports and destinations are only briefly touched in "Hetzner Cloud (and probably others)", as there are specialities for Hetzner.

Can we have a chapter that deals with outgoing destinations and ports during installation and operation?
E.g. for http/https towards GitHub (git clone), DNS towards root server and recursive resolution, etc.?

I think not every Mailcow instance is placed on the internet with the firewall completely open for outgoing connections.
For such installations, an overview of the required connections would be helpful.

Greetings
Stefomat

[Niklas Meyer]

If you want to contribute that feel free to do so. Right now it's not planned to implement such information from our side.