What can I do if I get repeated Office 365 password prompts from a Hosted Exchange Mailbox?

For repeated password prompts in Outlook where Outlook is trying to connect to Office 365 rather than Hosted Exchange the below registry key needs to be added:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\AutoDiscover\
DWORD: ExcludeExplicitO365Endpoint
Value: 1

Versions of Outlook older than 2016 may have a different value instead of 16.0 in the registry key above. Outlook may need to be restarted for the change to be applied.