Outlook 2016 Office 365 password prompt error

Do you (or did you) have an old onsite Exchange server? I found that when Outlook was prompting for a password and not accepting my valid Office 365 account, it was actually because Outlook had decided to reconnect to our old Exchange server.

Here's my writeup on how to check your Active Directory for old Service Connection Points:

http://soniacuff.com/outlook-2013-changes-account-from-office-365-to-old-on-premise-exchange-server/

-Sonia