Apart from OLM files, Mac Outlook creates temporary files in the backend called as OLK file. OLK15message file are backend email files of Outlook 206 for Mac. OLK15message files is a safety precaution measure taken by the outlook for mac if your database or emails get corrupted. What is an OLK15message file and how is it related to Outlook 2016 for Mac? How can OLK15message files be used to recover data? How is it. The OLK15message file, contains the email's header information and also the email body contents, but also stored separately, in other words. What is OLK14Message and OLK15Message Files?.