by lunarg on August 20th 2015, at 16:26

The way public folders work has been changed radically in Exchange 2013. Starting from Exchange 2013, public folders are basically stored in a regular mailbox, and then published as public folders. With Exchange 2010 being the last version to support so-called "legacy" public folders, Exchange 2013 is not able to access these folders. As a consequence, if you're in the middle of a migration from Exchange 2007/20102010 to 2013, or are running a mixed environment, and you still have these legacy public folders on your Exchange 2010, you will notice that users with a mailbox migrated on Exchange 2013 will no longer be able to access these public folders. As Exchange 2013 no longer supports "legacy" public folders, the old method of accessing them is no longer valid.

Luckily, you can re-enable access to these public folders through the use of a so-called proxy mailbox. This is a regular user mailbox which will act as a "gateway" to the legacy public folders. This proxy mailbox will then be configured as a remote public folders container on Exchange 2013, resulting in Exchange 2013 (and all clients) to have access to the legacy public folders.

Note that this is only a temporary workaround. If you decide to decommission your Exchange 2007/2010 environment, you will have to migrate the legacy public folders to an actual mailbox that is configured as the public folder root mailbox on Exchange 2013. But this is outside the scope of this article.

This article does not provide you with a solution to get legacy public folders running on your Exchange 2013 servers. You will still need an Exchange 2007 or 2010 CAS server to access legacy public folders. In an Exchange 2013-only environment, you'll need to use the new method for using public folders. This is also outside the scope of this article.


  • At least one Exchange 2013 must have CU5 or higher. The cmdlets mentioned in this article that need to be run on a 2013, will have to be run on a server with CU5 or higher.
  • All Exchange 2007/2010 mailbox servers that have a legacy public folders database also require the CAS role to be installed. They do not have to be part of a client access load balancing if one is present in your environment.

Configuring access to the legacy public folders

Enable access to legacy public folders on Exchange 2007/2010 from Exchange 2013

Perform these steps on each server containing a legacy public folder database:

  1. Create a new empty regular mailbox database:
    Exchange 2010:
    New-MailboxDatabase -Server <PFServerName_with_CASRole> -Name <NewMDBforPFs> -IsExcludedFromProvisioning $true -EdbFilePath <PathToEDBFile> -LogFilePath <PathToDirContainingLog>
    Exchange 2007:
    New-MailboxDatabase -StorageGroup "<PFServerName>\<StorageGroup>" -Name <NewMDBforPFs>
  2. Create a proxy mailbox in the newly created mailbox database and hide it from the address book. The primary SMTP address of this mailbox will be returned through autodiscovery as the DefaultPublicFolderMailbox so the client knows which mailbox to connect to to get to the legacy public folders.
    New-Mailbox -Name <PFMailbox1> -Database <NewMDBforPFs> 
    Set-Mailbox -Identity <PFMailbox1> -HiddenFromAddressListsEnabled $true
  3. Exchange 2010 only!
    Configure the mailbox database containing the proxy mailboxes so the Exchange 2007/2010 is explicitly used to access the database by configuring the client access server of the database.
    Set-MailboxDatabase <NewMDBforPFs> -RPCClientAccessServer <PFServerName_with_CASRole>
    This step is not required on Exchange 2007.

Configure proxy mailboxes as public folders

To have Exchange 2013 access the legacy public folders, we need to configure the proxy mailboxes that were created as remote public folder mailboxes. This enables Exchange 2013 to use these proxy mailboxes as "gateways" to the real legacy public folders on the Exchange 2007/2010 servers.

  1. Configure the proxy mailboxes to act as remote public folder mailboxes:
    Set-OrganizationConfig -PublicFoldersEnabled Remote -RemotePublicFolderMailboxes ProxyMailbox1,ProxyMailbox2,ProxyMailbox3
    All proxy mailboxes will have to be added to the list in this manner. Mailboxes that are not added will not be available as public folders.
  2. Wait for Active Directory synchronization to complete. This may take up quite a bit of time, depending on the AD topology of your environment.

Verify access to public folders in Outlook

To verify you can access the public folders in Outlook, perform the steps below on a client whose primary mailbox is on an Exchange 2013 server:

  1. Start Outlook.
  2. In the system tray, right-click the Outlook icon while holding down CTRL on your keyboard. Then click Test E-mail Auto Configuration....
  3. In the dialog, click the Test button and wait for it to complete.
  4. Click the XML tab and look for the following information:
    <SmtpAddress><SMTP Address for public folder mailbox</SmtpAddress>
    If the information is not present, then either Active Directory has not finished replicating, or there's an error somewhere in your configuration.
  5. Verify you can access the public folder hierarchy, check permissions and perform tasks according to the permissions set for the user logged in on Outlook.


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