
At this point, it is clear that Microsoft has a significant syncing issuing with Gmail and, while there are temporary workarounds (see above and below), I would avoid using a Microsoft email client to access your Gmail at this time.

In addition to this, reports are also growing of similar problems now occurring between Outlook and Gmail - both on Windows and Mac ( 1, 2.

06/28 Update: this problem appears to be getting worse with numerous threads now appearing on the Microsoft Communities forum citing Gmail email being lost, deleted or sent automatically to spam by the Windows 10 Mail app ( 1, 2 3, 4 5, 6, 7, 8 9, 10, 11, 12, 13, 14, 15, 16, 17, etc).
