Office 365 Custom User Agent
Learn how Microsoft Office 365 Custom User Agent changes after the upgrade.
|App sign-on policy rules with a Custom User Agent (as a client application) don't migrate fully. The Custom User Agent String is lost after migration and can't be recovered.
|You need to add the user agent to the authentication policy rule after the upgrade has been completed, and then activate the rule.
|Allow or deny custom clients in Office 365 sign-on policy