Next, use your email program to import the mbox format. In the case of Thunderbird, this has to be done manually at the moment. To accomplish this, open the ~/Library -> Thunderbird -> Profiles -> default -> random_string.slt -> Mail -> Local Folders folder. Drop the mbox files in there and you're set.
The same works for Mozilla, where the mail folder resides in the ~/Library -> Mozilla -> Profiles -> default -> random_string.slt -> Mail -> Local Folders folder.
The same technique should exist for apple mail. Good luck trying!

