Help an old man

So I’m slowly considering ceasing using command-line mail software in favor of a GUI mailer like Thunderbird. I have one sticking point, however. Right now, I have a huge archive of old mail… It is very well organized; I have a mail/Saved folder and inside that folder I have hundreds of mbox files which are gzipped. Mutt can deal with these gzipped folders on the fly..

Now, say I want to use Thunderbird as my mailer, and I want to advertise all of these folders through IMAP, and be able to create new folders as needed over IMAP, how do I do this.. I realize I might have to give up on the gzipped folders, which is fine by me, that’s what I pay dues for at CSH, but it seems that the only way to get folders to show up is to make sure they are listed in ~/.mailboxlist, which I am completely disinterested in maintaining. I know there has to be a “proper” way of doing this, I just don’t know what it is… Can anyone provide any insight/articles on the right way of handling all this stuff?