XADM: Recipient Update Service Creates Duplicate Secondary SMTP Addresses That Causes Non-Delivery Reports

If the Active Directory Connector (ADC) Connection Agreement between Exchange Server 5.5 and Active Directory is one way, the Recipient Update Service may create duplicate SMTP addresses. When this happens, the changes in Active Directory are never replicated back to Exchange Server 5.5, and therefore, the two directories become unsynchronized, causing mail to generate non-delivery reports (NDR).

To resolve this problem, obtain the latest service pack for Microsoft Exchange 2000 Server. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
There are two ways to avoid this problem:

• For the two directories to remain synchronized, only use two-way Connection Agreements.
• If using only two-way Connection Agreements is not possible, exclude the default recipient policy for the Exchange Server 5.5 site from applying to the Exchange Server 5.5 users that are replicated by the ADC. To do so:
  
  
  1. In the Users and Computers MMC snap-in, click a user.
  2. Right-click the user, and then click Properties.
  3. Click the E-mail tab.
  4. Click to clear the Automatically update e-mail addresses based on recipient policy check box.
  Or you can write a script that excludes that Recipient policy from applying to sites with a one-way Connection Agreement.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Microsoft Exchange 2000 Server Service Pack 2.