qpsmtpd is very stable software that is leisurely developed. New releases are as-needed.
Releases: GitHub Releases
See the Change Log
You can also get qpsmtpd with Git.
Many users have custom `forks` with their particular changes. If you go that route it's highly recommended that you fork from git to make it easier to contribute.
git clone git://github.com/smtpd/qpsmtpd.git
You can browse the repository.
qpsmtpd has been used for the primary perl.org mail servers since 2001. Apache.org also uses qpsmtpd. Years ago a happy user wrote and told that qpsmtpd is rejecting several hundred thousand spams a day on his server; these days that's too common to be exceptional.