Some of you may be interested in this... I decided I wanted to hack on node.js to see what all the fuss is about.
So to do that I have basically ported Qpsmtpd to Node.js (and given it a decent name while doing so!).
It's still early days - there are no plugins to speak of yet (i.e. no queue plugins at all yet), but you might be interested in just looking anyway:
https://github.com/baudehlo/Haraka
