The SMTP mail server for the 21st century and onwards is OpenSMTPD, which is developed as an integral part of OpenBSD, but available in a portable variety too.

It was one of those things that I had fully intended to do years ago, but I only got around to actually doing once there was a definite deadline to get it done.

The time has come, as OpenBSD 7.9 will leave the exim package behind, and exim users will need to find a replacement before upgrading. This article describes my transition to OpenBSD's own OpenSMTPD mail server.