All you need for mac mail backup and archiving is the Mail Backup X for Mac. It is applicable not only to Outlook but also Gmail, Hotmail, Thunderbird, Postbox, Yahoo Mail etc. It can also import files sent by those mail clients- .eml format, .olm archive etc. It comes with a mail converter engine for the sake of clients who need to change the format of their files in order to transfer them to a different device. Transportation of files is made easier with PDF conversion of them.