Microsoft KB Archive/169781

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Knowledge Base

XFOR: IMC Fails to Send Mail to Domains with Multiple MX Records

Article ID: 169781

Article Last Modified on 10/28/2006


  • Microsoft Exchange Server 4.0 Standard Edition
  • Microsoft Exchange Server 5.0 Standard Edition

This article was previously published under Q169781

IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information on how to do this, view the "Restoring the Registry" online Help topic in Regedit.exe or the "Restoring a Registry Key" online Help topic in Regedt32.exe.


This problem occurs when you send SMTP messages through the Internet Mail Service (or the Internet Mail Connector [IMC], in version 4.0) to domains with multiple MX records. The message stays in the outbound queue waiting delivery, gets name resolution, and then times out, and a non-delivery report (NDR) is returned. This problem is usually encountered when sending messages to large corporations.

The following error message may be received when you get information on the messages sitting in the queue:

421 NSO Unable to contact destination SMTP demon


To work around this problem:

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall Windows. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And Values" online Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" online Help topics in Regedt32.exe. Note that you should back up the registry before you edit it.

  1. Add DisableResolverSearchList to the following registry key:


    DisableResolverSearchList is added in the

    For more details on this process refer to 150969.

  2. Use NSLookup to get the correct IP addresses for the correct MX records of each E-Mail Domain.
  3. In the IMC \ IMS Connections property tab, click on the E-Mail Domain command to specify Message Delivery by E-Mail domain.
  4. Enter one Domain name- IP address pairs for every MX record found in step 2.
  5. Repeat steps 3 and 4 for every other domain that has having multiple MXrecords and is experiencing this problem.
  6. Send a message to each one of these domains to test the workaround solution.

Keywords: kbprb kbusage KB169781