Outlook continually prompts for password
A couple of solutions which are off the well beaten track: 1. You are in a hybrid environment with an on-premises mailbox but an E3/E5 license applied to your user. Exchange Online spontaneously creates a mailbox. (Workaround for this is to remove the Exchange Online sublicence along with the licenses which depend on it - you just have to remember you did that when you migrate to EXO down the road...) 2. You have an old group policy or settings reg file which you think is aligned with MS365 norms but contains the following key - delete it, or change it to Delete in the Group Policy Preferences if it is a wider issue. Computer\HKEY_CURRENT_USER\SOFTWARE\Microsoft\Exchange DWORD MapiHttpDisabled 1 https://learn.microsoft.com/en-us/outlook/troubleshoot/connectivity/outlook-not-connect-exchange-use-mapi-over-http