I don’t know if this is considered OT, but dovecot has support for sieve. I had a rule set running under Mac OS X 10.8.5 Server 2.2.5 which I did maintain by hand on the server because a while before Mac OS X Server had dropped support for Squirrelmail.

Now I wonder if there is a decent way to get sieve running again on macOS 10.12 Sierra with Server 5.2

G