I just found this thread because I can't rely on the built in N900 e-mail client and I am looking for an alternative. The IMAP support and a few other missing settings are a major show stopper, very disappointing.

So has anyone on this thread tried to compile Thunderbird yet? What happened?
What about mutt, I have not use a cmd e-mail client in years but I will switch back if that what it takes to get something decent.