I solved my routing problem... by switching to Exim. :)
Arbitrary routing decisions can be implemented by simply daisy-chaining routers in a config file. It's actually surprising how easy it is to read the whole logic at once just by glancing at one file. Almost like pseudo-code.
Their users list was also very helpful, and the overall tone of the discussion was friendly and non-dismissive towards this complete Exim newbie. That was a pretty stark contrast.
I've been using Postfix for over a decade now, and I thought I could do anything with it (provided that enough research and tests are performed), but I was amazed how much easier it was to solve a complex problem like this with Exim.
-- Florin Andrei http://florin.myip.org/
