Exchange Online users can't access legacy on-premises public folders

Applies to: Exchange Server 2010 EnterpriseExchange Server 2010 StandardExchange Online

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 For more information, see Office 365 Hybrid Configuration wizard for Exchange 2010.


You have a hybrid deployment of Microsoft Exchange Online in Microsoft Office 365 and on-premises Microsoft Exchange Server, and you've configured on-premises public folders in Exchange Server 2010 or Exchange Server 2007. These folders are also known as legacy public folders.

In this scenario, a user who was created in Exchange Online receives the following error message when she or he tries to access the legacy public folders:
Cannot expand the folder. The set of folders cannot be opened.
Network problems are preventing connection to Microsoft Exchange


This issue occurs if the mailbox for the user was created in Exchange Online and doesn't have an associated on-premises user object for authentication to the public folder.


For this issue to be resolved, the Exchange Online mailbox must be linked to an on-premises user account. For more information, see the following Microsoft Knowledge Base article:
2641663 How to use SMTP matching to match on-premises user accounts to Office 365 user accounts for directory synchronization


For more information, see the following Microsoft TechNet article:
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