XCON: No NDR When You Send Message to Invalid OR Address

• Microsoft Exchange Server version 5.0

SYMPTOMS

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

CAUSE

When a message is sent to a manually entered X.400 O/R address (referred to as an one-off routing address) that is invalid, 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 as for an X.400 proxy). The message is submitted to the message transfer agent (MTA). During message submission to the MTA, the store checks the syntax but not the "routability" of the message.

As expected, this message causes the remote MTA to generate an NDR. As this NDR reaches the sender's store, the same code path is taken for entry ID 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):

   S E R V P A C K

MORE INFORMATION

With the fix in place, the parsing code skips the check on length and syntax of the O/R address in the NDR.