Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine whether the maximum size for delivery status notification (DSN) messages has been set:


The Exchange Server Analyzer also queries the Active Directory® directory service to determine the value of the serialNumber attribute for all objects with an object class of msExchExchangeServer. If the string value includes "Version 5.5," the computer is running Microsoft Exchange Server 5.5. If the string value includes "Version 6.0," the computer is running Microsoft Exchange 2000 Server. If the string value includes "Version 6.5," the computer is running Microsoft Exchange Server 2003.

If the Exchange Server Analyzer finds that the MaxDSNSize registry value does not exist on a computer that is running Exchange 2000 Server or Exchange Server 2003, a warning is displayed.

The MaxDSNSize registry value is an optional value in Exchange Server that limits the size of DSNs. This option configures Exchange to remove attachments if a message cannot be delivered. If you add this registry value, it is recommended that a value of 10240000 bytes (10 megabytes) be used.

The MaxDSNSize registry value was introduced in Service Pack 2 (SP2) for Exchange 2000 Server, and therefore requires Exchange 2000 Server SP2 or later versions to work. Additionally, in Service Pack 1 for Exchange Server 2003 and later versions, a value of 10 megabytes is used in the absence of the MaxDSNSize registry value. If you want, you can add the MaxDSNSize registry value to override this default behavior.

If you enable this option, you can save server and network resources. However, there are drawbacks to this implementation of Simple Mail Transfer Protocol (SMTP) attachment stripping. If you enable this option to strip the attachments from the non-delivery report (NDR), the details that are necessary to display the notification in the preview pane are also stripped, and the originator of the message cannot use the Send Again option. If the originator of the message tries to use the Send Again option from the NDR, the originator of the message receives the following error message: Unable to resend the message. The nondelivery report does not contain sufficient information about the original message. To resend the message, open it in your Sent Items folder, click the Actions menu, and click "Resend this message".

However, the originator of the message cannot resend the message, even by using the method in the error message.

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\System\CurrentControlSet\Services\SMTPSvc

  3. Right-click SMTPSvc and select New | Key. Name the new key Queuing and leave the class blank.

  4. Right-click Queuing and select New | DWORD Value. Name the new value MaxDSNSize.

  5. In the right pane, double-click the MaxDSNSize registry value and enter the size limit (in bytes) that you want in the Value data field. Messages that are larger than this value that generate an NDR do not return attachments or full message properties.

  6. Close the registry editor, and then restart the Simple Mail Transfer Protocol (SMTP) service for the change to take effect.

For more information about the MaxDSNSize registry setting, see the following Microsoft Knowledge Base articles: