I did try IMP before ending up on Squirrel. I ran into problems just getting the thing up and running. It had too many prerequisites to get it to run, which is a shame because it looks good. I didn't really want to mess around installing (and in some cases updating) too many components as I'm running it on my mail DNS/mail server...

Squirrel in comparison was much easier to get running (only took 15 minutes).
_________________________
Remind me to change my signature to something more interesting someday