XCON: No NDR on Malformed X.400 Addresses

• Microsoft Exchange Server version 5.0

SYMPTOMS

When a message is sent to an invalid originator/recipient (O/R) address, a non-delivery report (NDR) is generated, as expected. However, the NDR is never delivered to the originator of the message.

CAUSE

When a message is sent to an invalid, manually entered X.400 O/R address (referred to as an one-off routing address), the store uses Address.dll to normalize the O/R address. The normalizing process consists of ordering the attributes in the O/R address which is in the form of a string. This ordering is important so that the address can be resolved to a DN (just like for a X400 proxy). The message is submitted to the MTA. During message submission to the MTA, the store checks the syntax but not the "routability" of the message.

As expected this message will cause the remote MTA to generate an NDR. As this NDR reaches the sender's store the same code path is taken for entryid generation for the actual recipient name. The store now proceeds to parse the NDR and encounters the attributes that refer to the actual recipient of the original message. It fails to parse these and proceeds to drop the NDR.

STATUS

Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 5.0. This problem has been corrected in the latest U.S. Service Pack for Microsoft Exchange Server version 5.0. For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

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