[bsdice]

Took me weeks to perfect our own setup based on Postfix, Dovecot, Roundcube with some patches, rspamd with attachment-type whitelisting and a bazillion other features, clamav with extra patterns, plus the many tweaks and enhancements you need to dig out from obscure places.

Like fts-flatcurve, an archive plugin for dovecot that can find stuff in 30 years worth of mails in a second, over IMAP in Roundcube. Or rspamd settings to blacklist not a single IP but an entire ASN of misbehaving colo clients. IMAP with namespaces is also a true pain to configure. Or setting bzip2 compression for an auto-expunged journal for spam, and archive without expunge. Painful.

If you made it this far, you will find that your IP address is tainted. So choosing a hoster that keeps his backyard clean from spammers is necessary, otherwise you will suffer by association. Did I mention SPF records in DNS.

So I consider our server a piece of art. 30 years in operating systems certainly helped.