On-premises Exchange 2003 and Outlook 2003 users can't view free/busy information of Office 365 users in a hybrid deployment

You have a hybrid deployment of on-premises Microsoft Exchange Server and Microsoft Exchange Online in Microsoft Office 365, and the following conditions are true:

• The on-premises server environment�is running both Microsoft Exchange Server 2010 and Microsoft Exchange Server 2003.
• The Exchange 2003 public folder is set up to use a custom list instead of routing groups for public folder referrals.

In this scenario, on-premises users who have a mailbox on Exchange 2003 or who are using Microsoft Office Outlook 2003 can't view the free/busy information of Office 365 users. However, they can view the free/busy information of other on-premises users. Additionally, on-premises users who have a mailbox on Exchange 2010 can view the free/busy information of Office 365 users.�

This issue occurs if Exchange 2003 cannot refer Outlook to the Exchange 2010 public folder server that contains the replica. Although an Exchange 2010 server is specified in the custom list for public folder referrals, the cost calculation fails. When the Exchange 2010 server is selected in the public folder referral custom list from the Exchange 2003 Management System, the public folder database is displayed instead of the server.

Exchange 2003 incorrectly resolves the Exchange 2010 server in the list of public folder referrals to the GUID of the Exchange 2010 public folder database instead of the GUID of the Exchange 2010 public folder server. When Exchange 2003 looks up the database GUID to assign cost, it's not a valid server path. Therefore, it's marked with an infinite cost. Because the cost is infinite, Exchange 2003 doesn't refer the client to the Exchange 2010 server.

To resolve this issue, use Active Directory Service Interfaces Editor (ADSI Edit) to modify the msExchfolderAffinityList attribute on the server that is running Exchange 2003. Specifically, replace the GUID of the Exchange 2010 public folder database with the GUID of the Exchange 2010 public folder server.

To do this, follow these steps on the server that is running Exchange 2003.

1. Open Exchange Management Shell, and then follow these steps:
   1. Identify the GUID of the Exchange 2010 public folder database. To do this, run the following command:

      get-publicfolderdatabase |fl name, guid

   2. Identify the GUID of the Exchange 2010 public folder server. To do this, run the following command:

      get-exchangeserver |fl name,guid

2. Use ADSI Edit to locate the msExchfolderAffinityList attribute, and then specify the GUID of the Exchange 2010 public folder server.
   1. Open ADSI Edit, and then connect to the Configuration context.
   2. Expand the domain, and then locate the server. The path of the server is as follows:
      
      Configuration/Services/Microsoft Exchange/<OrganizationName>/Administrative groups/Servers/<ServerName>
      
      
   3. Right-click the server, and then click Properties.
   4. Click the Attribute Editor tab, locate and then select the msExchfolderAffinityList attribute.
   5. Click Edit, and then, based on the information that you obtained in step 1, replace the GUID of the Exchange 2010 public folder database with the GUID of the Exchange 2010 public folder server.
3. Restart the Microsoft Exchange Information Store service. For more info about how to do this, go to the following Microsoft website:
   How to Restart the Microsoft Exchange Information Store Service

After you follow this procedure, the Exchange 2010 public folder server name will be displayed in the custom list for public folder referrals. Be aware that you can modify the other servers in the custom list without affecting the updated GUID in the msExchFolderAffinityList attribute.

The msExchfolderAffinityList attribute is the Active Directory property that resolves the custom list for public folder referrals to server GUIDs.

For more information, see the following Microsoft resources:

• Microsoft TechNet article: Understanding Public Folder Referrals
• Exchange Team Blog post: Cross Org Availability using Federation Trust and Organization Relationship

Still need help? Go to the Office 365 Community website.