I recently changed my machine in work and thought that since everyone else is using MS outlook I should swap over and do the same. A while ago I went through a bunch of mail clients to try and figure out the best, and Mozilla Thunderbird was the one. Packed with loads of nice features and pretty good IMAP support I’ve been using it for a few months.
So now i decide to switch back, and damn, what a complete PITA. You can get your mail into thunderbird, but you can’t get it back out. In the end i had to use a program called IMAPsize to convert the thunderbird MBOX files into seperate EML files. The EML files then got pulled into outlook express, and once that was done, I could finally pull everything into outlook.
The whole thing took the best part of a day.