We have considered implementing this but the issue is that smtp is complex. This would need to be robust and should provide message queueing, async delivery, TLS, etc. IMO it's better to hand off the email to an external process that does the message delivery. Calling exec_async() to invoke /usr/bin/mail is just that, though I agree that this is a little ugly. Ideally this should be a cross-platform solution so that the same config would work on windows and *nix.