Try MacMister Mac Apple Mail Converter if you're looking for the best Apple Mail Converter Tool for Mac OS. It can successfully convert Mac Mail files, including emails, contacts, tasks, notes, calendars, journals, and more, to over ten different file formats, including PST, EML, MSG, IMAP, Gmail, Thunderbird, MBOX, HTML, PDF, DOC, and Office 365. Additionally, the program makes it simple and error-free to export individual Apple Mail emails as well as bulk emails. All versions of macOS, Outlook, and Windows OS operate flawlessly with this program.