Another good guide that uses Debian and its standard packages:
* https://workaround.org/ispmail-trixie
(Updated with every release, and upgrade/migration instructions.)
https://www.iredmail.org
https://mailinabox.email/
I'd recommend mailcow for regular usage, or mailinabox if you're low on RAM or configuring email for server (not for people).
Another good guide that uses Debian and its standard packages:
* https://workaround.org/ispmail-trixie
(Updated with every release, and upgrade/migration instructions.)