You cannot view public folders that reside on a computer that is running Exchange Server 2003 or Exchange Server 2007 when you use Exchange Server 2010 Outlook Web App

When you use Microsoft Exchange Server 2010 Outlook Web App (OWA), you cannot view public folders that reside on a computer that is running Exchange Server 2003 or Exchange Server 2007.  Additionally, you receive the following error message:

The public folder you're trying to access couldn't be found. For more information, contact your helpdesk.

This issue occurs because all the following are true:

• Your mailbox resides on Exchange Server 2010.
• The public folders that you are trying to access do not reside on a computer that is running Exchange Server 2010.
• Exchange Server 2010 OWA cannot proxy requests for public folders that reside on a computer that is running Exchange Server 2003 or Exchange Server 2007.

 To resolve this issue, you must replicate the public folder content from Exchange Server 2003 or from Exchange Server 2007 to Exchange Server 2010. 

How to replicate the content of a single public folder

You can use Exchange Server 2003 or Exchange Server 2007 to create a replica of a single public folder on Exchange Server 2010.  To do this, follow these steps:

1. In Exchange System Manager, expand Administrative Groups, expand the Administrative Group for the Exchange 2003 Public Folders server, expand Folders, and then expand Public Folders.
2. Right click the folder that you want to replicate, and then click Properties.
3. On the Replication tab, click Add.
4. Add the Exchange Server 2010 public folders server that needs the replica, and then click OK for all windows.
5. Wait for replication to occur, or manually replicate. To manually replicate, follow these steps:
6. In Exchange System Manager, expand Administrative Groups, expand the Administrative Group for the Exchange 2003 Public Folders server, expand Folders, and then right-click Public Folders.
7. You can click Synchronize Hierarchy, click Resend Changes, or click both.
   
   Note The manual replication of public folders, even for a single folder, will not make the data immediately available.

 How to replicate all public folder content to Exchange Server 2010

If you want to replicate all public folders from Exchange Server 2003 or from Exchange Server 2007 to Exchange Server 2010, follow these steps:

1. On the computer that is running Exchange Server 2010, run the following cmdlet in the Exchange Management Shell:
   
   .\AddReplicaToPFRecursive.ps1 -server "<Name of Exchange Server 2010 server>" -TopPublicFolder "\" -ServerToAdd "<Name of Exchange 2010 Server>"
   
   Note In this cmdlet, the placeholder <Name of Exchange Server 2010 server> represents the name of the server on which you want to include a replica.  If you have multiple Exchange Server 2010 public folders servers, you can run the cmdlet for each server.
   
   
2. Replicate the Exchange Server 2003 or Exchange Server 2007 public folders hierarchy and content to computers that are running Exchange Server 2010 by using the Exchange Server 2003 Exchange System Manager or the Exchange Server 2007 Exchange Management Console.  
   
   To replicate the hierarchy and content from Exchange Server 2010, follow the instructions that are included in the following Microsoft TechNet articles:

Update a Public Folder Hierarchy

Update Public Folders

In Exchange Server 2010, when a mailbox resides on Exchange Server 2003 or on Exchange Server 2007, the OWA user receives the Exchange Server 2003 OWA or the Exchange Server 2007 OWA experience.  However, when the user's mailbox is homed on Exchange Server 2010, no requests are proxied to Exchange Server 2003 or to Exchange Server 2007 for public folders information. Only the Exchange Server 2010 OWA experience is available.

Resources

Public Folder Replication Troubleshooting � Part 2: Troubleshooting the Replication of Existing Data

Scripts for Managing Public Folders in the Exchange Management Shell