Availability (free/busy) fails for delegated mailboxes in Exchange hybrid deployments using Graph API only

Applies To
Exchange Server SE

Symptoms

In a classic hybrid deployment that's configured by using ConfigureExchangeHybridApplication.ps1 -UseGraphApiOnly, availability (free/busy) information fails when a remote mailbox user accesses a delegated on-premises mailbox and checks the availability of mailboxes that are hosted in Exchange Online.

When this issue occurs, you experience the following symptom, depending on the UI.

UI Symptom
Classic Outlook The following error message is displayed: “Your server location could not be determined. Contact your administrator.”
Outlook on the web (OWA) The following error message is displayed: “No information"
Exchange EWS logs The following error is recorded:

"The remote server returned an error: (403) Forbidden."
EXNL-GraphWebRequestProcessingException:WebException

Resolution

The issue has been fixed in the service.

  1. Check the current value of the EnableRouteThroughMSGraphFeature override, by running the following command:

    Get-SettingOverride -Identity EnableRouteThroughMSGraphFeature

    If it is set to Enabled=False, or if you had previously disabled the override, re-enable it by setting it to Enabled=True using the following command:

    Set-SettingOverride -Identity EnableRouteThroughMSGraphFeature -Parameters "Enabled=True"

  2. To apply the changes immediately, run the following command:

    Get-ExchangeDiagnosticInfo -Process Microsoft.Exchange.Directory.TopologyService -Component VariantConfiguration -Argument Refresh

More information

  • A remote mailbox is a mail user in Active Directory that's associated with a mailbox in the cloud service. For more information, see Set-RemoteMailbox.