Official documentation: Export to an Outlook for Mac Data File Backing up Outlook 2011 for Mac information using drag and drop to desktop
You will prompted with a file name (Outlook for Mac Archive.olm) and to save.Select the option for ' Outlook for Mac Data FIle (.olm)' and check all items to save everything.To make a local file archive of your Outlook 2011 for Mac information: This techinique has the advantage of storing your Outlook 2011 for Mac data into a single file for safe keeping or transfer to another Mac. See Backing up Outlook 2011 for Mac information using Export Feature Mac users can use Apple's Time Machine to backup their data to an attached external drive or another disk partition (Apple does not support network drives). Outlook 2011 for Mac data can be backed up in a number of different manual and automated methods.
