Error message when Exchange users try to access public folders that are hosted on Exchange Server 2003 by using Outlook Web Access for Exchange Server 2007: "Outlook Web Access is unable to open public folders"

In an Exchange Server 2007 and Exchange Server 2003 mixed environment, all public folder stores are hosted on Exchange Server 2003. When Exchange Server 2007 users try to access public folders by using the Outlook Web Access client, users cannot access these public folders. Additionally, the users receive the following error message: However, users can access the public folders by using Outlook clients.

The Client Access Server (CAS) role of Exchange Server 2007 always tries to access the public folder store by using the RPC protocol. This is by design on Exchange Server 2007. However, Exchange Server 2003 does not handle these RPC calls.

To resolve this problem, download Update Rollup 4 for Exchange Server 2007 Service Pack 1. Then, install the update on the Exchange server. For more information about how to download Update Rollup 4 for Exchange Server 2007 Service Pack 1, click the following article number to view the article in the Microsoft Knowledge Base:

For more information about how to enable users to access Public Folders from Outlook Web Access, visit the following Web site:

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.