Article ID: 2788136 - View products that this article applies to.
When Microsoft Outlook users try to access public folders in Exchange Server 2013, the following dialog box appears:
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However, if the users click Ok in this dialog box, they are not connected to the public folder.
Additionally, the users may receive the following error message:
Cannot expand the folder. The set of folders cannot be opened. The file C:\Users\<username>\AppData\Local\Microsoft\Outlook\filename.ost is in use and cannot be accessed. Close any application that is using this file, and then try again. You might need to restart your computer.
This issue occurs because the AutoDiscover service cannot discover the email address that is stamped on the public folder mailbox.
To resolve this issue, use one of the following methods:
The public folder database concept is removed from Exchange Server 2013. The public folders are now stored in a new kind of mailbox that is known as the Public Folder mailbox.
The Outlook client depends on information that is returned by the AutoDiscover service to access the Public Folder mailbox.
The following is an example of Public Folder mailbox information that is returned by the AutoDiscover service:
In this example, the Outlook client tries to "AutoDiscover" PFMailbox@contoso.com. However, if the DNS records that are related to Contoso.com are not present, Public Folder access fails.