Hello Tech Discussion community!

So my manager recently sent me 5 olk15message files exported from his Mac Outlook. He needs to me find a way how to decode these files so I can get important info from them. I tried installing several programs on my Windows 8 (Systools mainly) but to no avail.

May I ask if anyone here has other suggestions/means/programs they can recommend to me so I can successfully decode and read these olk15message files?