> But there are other solutions out there like: Stalwart; Mailcow ;Or if you're a purist you can set up your whole server yourself

Another good guide that uses Debian and its standard packages:

* https://workaround.org/ispmail-trixie

(Updated with every release, and upgrade/migration instructions.)

Some out of the box solutions.

https://www.iredmail.org

https://mailinabox.email/