Sorry for the late reply, but it's a pretty standard (imo) setup with postfix, dovecot, spamassassin, postfixadmin.

I'm planning to redo this soon (been a few years) and I'm as of yet undecided if I just do it manually again (like I do every 3-5 years) or if I'll use some template ala sovereign, mailinabox, mailcow, modoboa.

Also check this thread from last year: https://news.ycombinator.com/item?id=16238937