I'm trying to help someone that is using a newish Outlook version, to read their emails from Gmail. I think the method is set as IMAP, rather than POP. The problem is that when Outlook is opened, the bar at the bottom says syncing and it never stops, even after overnight session. Another symptom is that new email cannot be received.
After some googling, (going to visit soon), I'm just putting a few links here which may be helpful.