You have a mixed Microsoft Exchange Server 2010 and Microsoft Exchange Server 2003 environment. Or, you have a mixed Exchange Server 2010 and Exchange Server 2007 environment.
In this environment, users try to use Microsoft Outlook Anywhere to open a shared mailbox.
The shared mailbox was moved to Exchange Server 2010.
The user's primary mailbox is still hosted on the Exchange Server 2007 server or on the Exchange Server 2003 server.
In this scenario, the attempt to open the shared mailbox is unsuccessful. Additionally, the users receive the following error message:
Unable to open email folder
This issue occurs because the user is still connected to Exchange Server 2003 or to Exchange Server 2007 when he or she uses Outlook Anywhere. However, Exchange Server 2003 and Exchange Server 2007 do not register the Exchange Server 2010 servers under the ValidPorts registry key. Therefore, if the user tries to open a shared mailbox on an Exchange Server 2010, the operation fails.
To resolve this problem, change the URL of Outlook Anywhere in the Use this URL to connect to my proxy server for Exchange box to point to the new URL for Exchange Server 2010. For more information about how to configure a URL in Outlook Anywhere, visit the following Microsoft Web sites:
Microsoft Exchange Server 2010 Enterprise, Microsoft Exchange Server 2010 Standard, Microsoft Exchange Server 2007 Enterprise Edition, Microsoft Exchange Server 2007 Standard Edition, Microsoft Exchange Server 2003 Enterprise Edition