The mbox source format in Aid4Mail will work for Apple Mail, but there is a trick to it.
The .mbox "files" that Apple Mail exports to are not really files at all. They're folders. Inside the folder you'll find the real mbox file, usually just called "mbox". That's the file you need to process.
However, even better than that, Aid4Mail can process Apple Mails native file format, EMLX. That means you don't have to export to mbox at all. Just use the "Apple Mail" option on Aid4Mail's Mail Source screen.
If you experience any issues, don't hesitate to contact us.
If you would like to buy an Aid4Mail license, visit the Aid4Mail website.