@jherazob @mwl Largely software agnostic, and essentially OS agnostic (you could do this on any OSS stack without needing to seriously considering buying a different book).

It uses Postfix, Dovecot, rspamd and a few others, but the author takes painstaking care to explain WHAT needs to be done, then gives examples in HOW to do this in the given software, but also isn't afraid to say things like "You'll need to spend some time familiarizing yourself with rspamd to be successful -- here's how I do that. Go do that so you can do X, Y, or Z as appropriate for your situation."

You should have limited difficulty replicating this in comparable software, though it will be more straightforward of course if you make the same choices.