Unresolved sender for delivery status notifications (DSN) message after you install update rollup 7 for Exchange Server 2007 Service Pack 1

The behavior of hidden mailboxes has changed in Update Rollup 7 for Exchange Server 2007 Service Pack 1. As a result, hidden mailboxes in Active Directory are no longer resolved by Exchange Server. If an account that is used as the sender for Delivery Status Notifications (DSNs) is a hidden mailbox, delivery notifications will not show the display name "Microsoft Exchange" as the "From" address. Instead, delivery notifications will display the SMTP address of the system attendant, and this address will include the associated globally unique identifier (GUID).

To resolve this issue, install Update Rollup 8 for Exchange 2007 Service Pack 1.
For more information about Update Rollup 8 for Exchange 2007 Service Pack 1, click the following article number to view the article in the Microsoft Knowledge Base:

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