How to set up a mail server on a local network disconnected from the Internet?

Question

Debian

I have been running Axigen as a mail server for a long time, and in general, a trial license is no longer enough for me. I need to set up a normal mail server, but I can’t decide what to configure from, and most importantly, I’m confused about how. Tell me which solution should I use, I need the most convenient account management and preferably a web client. Can anyone suggest a worthy analogue of Axigen? Or a detailed manual on turnkey setup? I don't need spam protection and directing mail to the Internet, a peer-to-peer LAN without the Internet.

Answer 1

postfix
Manuals are full on the Internet