On-premises users can't consistently view free/busy information for Office 365 users in a hybrid deployment

Applies to: Exchange OnlineExchange Server 2010 EnterpriseExchange Server 2010 Standard
Note The Hybrid Configuration wizard that's included in the Exchange Management Console in Microsoft Exchange Server 2010 is no longer supported. Therefore, you should no longer use the old Hybrid Configuration wizard. Instead, use the Office 365 Hybrid Configuration wizard that's available at http://aka.ms/HybridWizard. For more information, see Office 365 Hybrid Configuration wizard for Exchange 2010.

PROBLEM

You have a hybrid deployment of on-premises Microsoft Exchange Server and Microsoft Exchange Online in Microsoft Office 365. However, on-premises users can't consistently view free/busy information for Office 365 users. On-premises users experience one or more of the following symptoms:
  • Free/busy information for Office 365 users is displayed for four to six hours, but the information isn't displayed after that time.
  • Free/busy information for Office 365 users is displayed as hash marks in the Scheduling Assistant in Microsoft Outlook.
On-premises users experience these symptoms even though the status in Outlook shows a successful connection to the Exchange 2010 public folder server, and the External (FYDIBOHF25SPDLT) public folder is already configured on the public folder server.

Additionally, the RPC Client Access logs on the public folder server show the following error message:

SOLUTION

On the Exchange 2010 hybrid server, change the permissions for the External (FYDIBOHF25SPDLT) public folder replica to Editor. For more information about how to do this, see the following Microsoft TechNet article:
Add Permissions for Client Users to Access Public Folder Content

MORE INFORMATION

This issue occurs if the default client permissions of the External (FYDIBOHF25SPDLT) public folder replica aren't set to Editor. By default, the permissions for the public folder replica are set to Author on the Exchange 2010 hybrid server.

If the permissions are set to anything that's lower than Editor, the RPC Client Access service on the Exchange 2010 public folder server can't write the availability information that the service retrieved from the federated organization to the External (FYDIBOHF25SPDLT) public folder replica.

For more information about cross-organization availability scenarios, see the following Exchange Team Blog article:
Cross Org Availability using Federation Trust and Organization Relationship
The Blog article discusses the steps to configure the External (FYDIBOHF25SPDLT) public folder. These steps are as follows:
  1. Make sure that there's an Exchange 2010 mailbox server that hosts a public folder database.
  2. If it's not already present, create a free/busy folder that's named External (FYDIBOHF25SPDLT), and make sure that the only replica of the folder is located on the Exchange 2010 server.
Note The free/busy folder is only created on a new Exchange 2010 installation when the option to create the public folders is selected during Setup. The option is available only if it's the first server that is installed in the organization. If a public folder database wasn't created during Setup, you have to manually create the folder. To manually create the folder, follow these steps:
  1. Connect to the on-premises Exchange 2010 public folder server.
  2. Open Windows PowerShell, and then run the following commands:
    • Add-PsSnapin Microsoft.Exchange.Management.Powershell.Setup 
    • Install-FreeBusyFolder
    After you follow these steps, a new Schedule+Free/Busy folder that's named External (FYDIBOHF25SPDLT) is created.

Still need help? Go to Microsoft Community or the Exchange TechNet Forums.