Intelligent Message Filter invalid custom response

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at]  

Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool reads the following registry key to determine whether the CustomRejectResponse registry value is present:


The Exchange Server Analyzer displays a warning if the following conditions exist:

  • The CustomRejectResponse value is present.

  • This value string does not start with 550 5.7.1.


    The response string value must start with 550 5.7.1 to be recognized as valid.

Exchange Server 2003 Service Pack 2 (SP2) allows for customization of the server response string that is generated and appended to the non-delivery report (NDR) sent back to the sender. The default response of 550 5.7.1 Requested action not taken: message refused can be changed to provide blocked legitimate users with a meaningful explanation as to why their message was blocked. This explanation can help reduce investigation of false positives and decrease support costs associated with the anti-spam processing.


This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore the registry if a problem occurs. For information about how to restore the registry, view the "Restore the Registry" Help topic in Regedit.exe or Regedt32.exe.

To correct this warning

  1. Open a registry editor, such as Regedit.exe or Regedt32.exe.

  2. Navigate to: HKLM\Software\Microsoft\Exchange\ContentFilter

  3. In the right task pane, right-click the CustomRejectResponse value and select Modify.

  4. Enter the string value you want to use as the custom response, starting the string with 550 5.7.1. For example, you can enter 550 5.7.1 Domain not an allowed sender to set the string to a valid string that will be appended to the NDR.

  5. Save the changes, exit the registry editor, and restart the SMTP service for the changes to take effect.

Before you edit the registry, and for information about how to edit the registry, see Microsoft Knowledge Base article 256986, "Description of the Microsoft Windows registry" (

For more information about intelligent message filtering, see the Exchange Intelligent Message Filter Web site (

For detailed information about how to perform intelligent message filtering tasks, see "Configure Intelligent Message Filtering" in the Exchange Server 2003 SP2 online Help.