You perform a monitoring latency test on an external email address by using the Test-Mailflow command on a Microsoft Exchange Server 2007 server. In this situation, the command returns a Success response for this test if the external email address is invalid or nonexistent.
This issue occurs because a relayed delivery status notification (DSN) is treated as a positive DSN in Exchange Server 2007.
To resolve this issue, install the following update rollup:
2407025 Description of Update Rollup 2 for Exchange Server 2007 Service Pack 3
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 Test-Mailflow command, visit the following Microsoft website: