If you’ve had it with Mail.app but haven’t switched to Thunderbird because you spent so long setting up all your mailboxes and dread the thought of redoing it, MacOSXHints has some good news for you. As of last nights build, Thunderbird will let you import any mailboxes you’ve set up in Mail.app. You’ll probably want to back everything up before trying this though.

Go to your Mail.app Library folder, usually located in your user’s Library -> Mail -> *your default account*. Make a copy of the inbox.mbox (perhaps to the desktop), then control click on the copied inbox.mbox and select Show Package Contents. Locate the file called “mbox” and change its name to “inbox.” Run Thunderbird, and set up an account (the same as the account in your Mail.app).

Close Thuderbird and navigate to the default user’s mailbox, which is normally in your user’s Library -> Thunderbird -> Profiles -> Default -> [random_string] -> mail -> *your mail account*/. Overwrite the inbox file with the file you’ve just changed in the Inbox.mbox. This worked for me, although I can’t confirm any attachments. I guess you could do this for all your accounts / drafts / outboxes / archives as well, to restore all your old emails. Obviosuly if it fark’s your machine - I take no responsability, but I hope it helps some people. I’m now going to convince my director we should be running TB on all clienst (open-source rocks).