thunderbird
I'm using thunderbird for quite some time now ( 0.2 I guess ) and I've never "compacted" any folder! Actually I thought it might compress it or something like that =) I guess I read it too fast the first time because I never realized that it's not compress... So for all out there who are using thunderbird and don't know that it's for: When you delete a mail in thunderbird it just doesn't get deleted but only marked for deletion! So each spam mail you got since you started using thunderbird is still saved! It just gets deleted when you compact a folder! So just start your thunderbird and do it! There have been 350 MB mails marked for deletion on my laptop!