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Hashed lines shown in scheduling assistant when Exchange Server 2016 tries to retrieve free/busy information across untrusted forests

Original KB number:   4456243


Consider the following scenario:

  • You deploy Exchange Server 2016 in a cross-forest topology.
  • You configure availability service in untrusted forest to share free/busy information.
  • You use the Scheduling Assistant feature to view the free/busy information about another forest mailbox in Outlook.

In this scenario, you could only see "\\\\\\\" in the free/busy information. In addition, the Outlook on the web (previously known as Outlook Web App) client is also affected.


This issue occurs because the Exchange Server doesn't send the AvailabilityAddressSpace authentication header. Therefore, a "The request failed with HTTP status 401: Unauthorized" error message occurs.


To resolve this issue, install Cumulative Update 11 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016.


Learn about the terminology that Microsoft uses to describe software updates.