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 |
Workaround
To work around this issue:
To route the calls through EWS, disable the following override:
Set-SettingOverride -Identity EnableRouteThroughMSGraphFeature -Parameters "Enabled=False"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.
Microsoft is investigating this issue and will update this article as more information becomes available.