Microsoft KB Archive/152955

= XCON: MTA Prematurely Returns Messages w/NDR =

Article ID: 152955

Article Last Modified on 10/28/2006

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APPLIES TO


 * Microsoft Exchange Server 4.0 Standard Edition

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This article was previously published under Q152955



SYMPTOMS
A message is returned to sender with a Non-Delivery Report (NDR) after only one attempt at sending from one MTA to another MTA using an X.400 connector. When the MTA on the other side is down, the message is expected to sit in the queue and to be retried based on the settings under Connection Retry Values on the Override tab on the X.400 connector property pages.



CAUSE
The problem occurs for messages sent to address spaces that have only one possible route, but for which the connector used can be involved in multiple routes for other address spaces. A quick test, (that is, "Does the connector have any alternate routes?") is initially used to decide whether or not to reroute a message. The full reroute processing for a message then uses the actual address space of the message to determine if an alternate route is available. (A connector may be the only route for address space X, but may be one of many possible routes for address space Y).

During reroute processing of a message with just one possible route, the route history is kept incorrectly. The second time the message goes through through reroute processing it behaves as though :
 * this message has just been transferred in.


 * the message has already traversed the destination MTA.

The "Routing loop prevention" function then prevents the message from being routed to the destination MTA; no other routes are available and so the message is returned with an NDR.



STATUS
Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 4.0. This problem was corrected in the latest Microsoft Exchange Service Pack. 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

Keywords: kbnetwork KB152955

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