I feel it's useful to bump this thread, since I have been having this exact problem on and off for several (at least 5) years. It's currently occurring again, and this prompted me to look into it (again?). As stated by others above, I am also receiving the following randomly when an Outlook mailbox update occurs (automatic or manual):
Task 'xxxxxxxxxx@msn.com - Receiving' reported error (0x800CCC92) : 'Your email server rejected your login. Verify your user name and password for this account in Account Settings. The server responded: -ERR Logon failure: unknown user name or bad password.'
As I said, this occurs randomly, about 1 out of 3 update attempts, although it is streaky. The other 2/3rds of the time, it works fine. Which means there's nothing wrong with my ID or password.
I am using Outlook 2016 MSO 32-bit, on Windows 10 pro. The account is set up for POP servers provided by MSN. I have two other email accounts on this installation that update with no problems (one a POP/SMTP hosted by Bluehost, the other a Hotmail Microsoft Exchange server).
Yet another occasion of Microsoft having a bug they can't diagnose even though it goes on for several years.