Symptoms
Assume that you deploy AD FS for single sign-on (SSO) by using Windows Server 2016 in Exchange Server 2016 environment. Then you set the value of ActivityBasedAuthenticationTimeoutInterval to less than 4 hours for device registration for users. When the time out value is reached, the Outlook on the web (formerly Outlook Web App) may sign out, and then enters an authentication loop. In this situation, users can't sign in to the Outlook on the web.
Cause
This issue occurs because the method that the Outlook on the web uses to request a new token from AD FS isn't correct.
Workaround
You can set the value of ActivityBasedAuthenticationTimeoutInterval to more than 4 hours. For example,
Set-OrganizationConfig -ActivityBasedAuthenticationTimeoutInterval 05:00:00
This example specifies the time span for signing out to 5 hours.
Resolution
To resolve this issue, install Cumulative Update 11 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
References
Learn about the terminology that Microsoft uses to describe software updates.
