Assume that you have a mailbox on an Active Directory site in a Microsoft Exchange Server 2010 environment. When you use a BlackBerry device to connect to a different Active Directory site, the Exchange server tries to proxy the connection. However, the server should redirect the request.
This issue occurs because the BlackBerry device is not in the redirect device list.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about the 451 redirect error, go to the following Microsoft website: