You use Microsoft Federation Gateway to configure a federation trust.
You create an organization relationship with another organization.
The organization has a subdomain that is in a mixed Microsoft Exchange Server 2003 and Microsoft Exchange Server 2010 environment.
A user who belongs to an Exchange Server 2003 server that is in the subdomain tries to view the free/busy information of a user in the other organization.
In this scenario, the user cannot view the free/busy information of the remote user.
This issue occurs because the Microsoft Exchange RPC Client Access service fails to search for the FederatedEmail.GUIDobject in the Active Directory. This occurs when the Exchange RPC Client Access service creates the Availability service request. The Exchange RPC Client Access service searches the domain controller in the subdomain where the Exchange server is installed. However, the Exchange RPC Client Access service should search the global catalog server in the root domain. Therefore, the Availability service request fails.
To resolve this issue, install Update Rollup 6 for Exchange Server 2010 Service Pack 1. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
2608646 Description of Update Rollup 6 for Exchange Server 2010 Service Pack 1
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about Federation, visit the following Microsoft website: