MICROSOFT CAN GO EAT A BAG OF DICKS!
I used a VPN earlier today & the email sensed this & the turds locked my account. I followed the process to unlock & identify the "unexpected usage," which went OK & I was able to log into the account online.
Except on this Mac, System Preferences>Internet Accounts & Mail both refused to accept the password, even when I changed it.
The only option has been to delete the email account from every device then re-add it to Mail. That restores access.
#FUCKEDOUTWANKERS
Had to remove the Mail account on the iPhone then add it again before it worked. but not the iPad, it accepted the new password. Go Figure.