The issue with most Unixy mail kits, is it's a collection of software that isn't always well coupled, and bundled together in really haphazard ways...

Many people want a simple interface that gives them administrative control (separate from physical accounts on the machine) that upgrades as a complete set...

With Unixy mail systems, you update dovecot, crap, something else breaks.. you have an older mysql backing it, crap, everything breaks when you upgrade... there's too many disconnected pieces for someone that isn't a full time mail admin to effectively keep up with.

I believe the original request is for something similar to say SmarterMail but open-source and free... something easy to setup, cross platform and packaged in a modern approachable language.... If I didn't have to work, I've often thought about doing something similar with Node.js