Update: Sadly OpenSMTPD version 5.4.4 on FreeBSD broke the passwd table, I’m checking the Gills to get this fixed.
I’m a big fan of Postfix and have been using it for years, but also find it to be an overkill for some of my servers. I don’t want to have to install Postfix on my DNS management server just to send change notifications. Sendmail was good for that for a while, but I hated the configuration language. Then I read that the OpenBSD maintainers switched to OpenSMTPD as their default MTA, so I decided to give it a shot.
It turned out to be a very nice piece of software; Small, fast, stable, and very easy to customize, no more ugly m4 macros to deal with :D. Now I have a Salt formula that installs OpenSMTPD, configures it to auto-start, and disables Sendmail. I use that for all non-mail servers for report and notification emails.