Apple Mail is one of the many email applications which uses MBOX file format to store its mailbox data. If you wish to migrate Apple Mail to Outlook, you require a professional software. And, the best one available is Kernel for MBOX to PST Converter. It can convert unlimited Apple Mail MBOX files to Outlook PST format in minimum time. You can download its free demo version to check its performance. http://www.applemailtopst.net/