Cross-forest or hybrid free/busy availability lookups fail in Microsoft Exchange Server

Original KB number:   2734791

Summary

Cross-forest or hybrid free/busy lookups fail when Microsoft Exchange Server can't retrieve availability data from the target organization. This problem typically occurs when the external URL for Exchange Web Services (EWS) isn't configured in the target environment. Without this URL, the Availability service can't locate or access the remote mailbox data. Configuring a valid EWS external URL restores free/busy lookups between organizations.

Symptoms

Cross-forest or hybrid free/busy information lookups fail in Microsoft Exchange Server. However, standard free/busy information lookups for users in the same forest work as expected.

Cause

This problem occurs if the external URL for Exchange Web Services isn't configured in the target forest.

Resolution

Configure the external URL for Exchange Web Services for the target forest. To do this, run the Set-WebServicesVirtualDirectory PowerShell cmdlet as shown in the following example:

Set-WebServicesVirtualDirectory -identity "server_name\EWS (Default Web Site)" -ExternalURL
https://mail.contoso.com/ews/Exchange.asmx

Note

In this command, contoso represents the actual domain name.

More information

Exchange Server uses the external URL for Exchange Web Services to connect to the target forest. Because the AutoDiscover service can't return the external URL for Exchange Web Services if Outlook Anywhere isn't enabled in the target forest, the cross-forest or hybrid lookup fails.

If either of the following cmdlets returns a value of $False, the mailbox isn't set to allow external connections by using Outlook Anywhere.

To verify that the mailbox is set to allow external connections by using Outlook Anywhere, run the Get-CASMailbox cmdlet as shown in the following example:

Get-CASMailbox <mailbox identity> | fl MAPIBlockOutlookExternalConnectivity