I do; a simple Debian/exim setup; it also has dovecot for imap access (only available over a tunnel). I've run it for a long long time (~20 years?) and it only

I do; a simple Debian/exim setup; it also has dovecot for imap access (only available over a tunnel). I've run it for a long long time (~20 years?) and it only needs the occasional tweak. It's had DKIM/SPF added and gone through a few combinations of anti spam filtering (post reception). It runs on the bottom level VM at a local hosting provider; when I started it they were providing UML! Originally resource usage was a challenge when subscribed to big lists - but these days even the biggest/highest bandwidth lists are no problem for it. And compared to gmail's flaky imap it's fast!