Outlook for Mac will automatically create an MBOX file for each folder you drag-and drop to the desktop. The simplest way to do this is to drag each folder of messages to the Mac desktop. If you want to migrate your Outlook for Mac mail to a Windows email program, first convert your Outlook for Mac mail folders to MBOX files. olm files from Microsoft Outlook for Mac, but it does handle the MBOX file format that Outlook for Mac supports.
