Error message when you use the Exchange Management Console to try to reconnect a mailbox to a user account: "The specified mailbox is not unique on database"

You have two or more disconnected Microsoft Exchange Server 2007 mailboxes that have the same legacyExchangeDN in a database. When you use the Exchange Management Console to try to reconnect one of mailboxes to a user account, the connection fails. Additionally, you may receive the following error message:

To resolve this problem, install Update Rollup 4 for Exchange Server 2007. For more information about Update Rollup 4 for Exchange Server 2007, see the following Exchange Help topic: For more information about how to install the latest Exchange service pack or update rollup, see the following Exchange Help topic:

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base: For more information about the naming schema for Exchange Server software updates, click the following article number to view the article in the Microsoft Knowledge Base: