[qsun]

node.js is Evented I/O. It might not be a perfect match for mail server. Not like in Comet or other similar situations, SMTP sessions are highly batched and not that human-interactive. There might be very little inactive open connections on a typical mail server.

But based on document, "Haraka's primary purpose is to provide you with a much easier to extend mail server than most available SMTP servers out there such as Postfix, Exim or Microsoft Exchange, yet while still running those systems for their excellent ability to deliver mail to users."