I've noticed Haraka (and I've used software by Matt Sergeant before, AxKit and qpsmtpd). I'm using qpsmtpd as the SMTP daemon already (that's how you do spam filtering in a Qmail setup, and qmail is the original delivery backend for qpsmtpd), which has the same architecture as Haraka (single process, event based, plugins). I haven't tried it, so I wouldn't know, but I'm still surprised that you suggest it is similar(?) to Qmail. It hasn't triggered my interest so far; I don't need raw speed for my purposes, and if I add a tool in another programming language then I might wait for a replacement in a language that allows for static verification (like Rust, Haskell, Ocaml) or has a process model built in (Erlang/Elixir); I know some MTAs already exist in those languages, although perhaps not stable or complete enough for me right now.
Perhaps let's stop or move this discussion elsewhere now as it's probably OT. I wanted to offer Tom my help, I didn't ask for help about MTAs here. Christian.
