Microsoft KB Archive/263924

= XCON: Message Transfer Agent Slows Down and CPU Usage Increases =

Article ID: 263924

Article Last Modified on 10/27/2006

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APPLIES TO


 * Microsoft Exchange Server 5.5 Standard Edition

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This article was previously published under Q263924



SYMPTOMS
When the Message Transfer Agent (MTA) processes messages, it may randomly slow down, and the percentage of the CPU used by the MTA may increase.



CAUSE
This behavior can occur if a distribution list is used to restrict the delivery of mail on X.400 connectors and connectors which contain the Internet Mail Service. The server on which the connector resides, and any server in the site on which this restriction has replicated are affected.



WORKAROUND
To work around this behavior, do not not use distribution lists to restrict the use of connectors.

If you need to use distribution lists to restrict the use of a connector, you may need to increase the memory or the number of processors on the affected computer. If you increase the  MTA registry parameter, you may also have to increase MTA performance.



MORE INFORMATION
To prevent the server from undergoing an inter-MTA hop, any server that has replicated the restriction data has its restrictions checked. This process is beneficial when sending large messages, but it can impede MTA performance if distribution lists are used to restrict usage of the connector. The MTA generates a Non-Delivery Report (NDR) for the message as soon as possible. If this restriction is not checked until the message reaches the connector server, the server must wait for the hop to the gateway before the check is performed. During this process bandwidth is wasted.

This design makes it is possible to check certain properties of all possible routes before you choose a link which contains costs and restrictions.

For additional information about delivery restrictions and low MDB users, click the article numbers below to view the articles in the Microsoft Knowledge Base:

158590 XCON: Delivery Restrictions Max CPU and Slow Down Message Delivery

176076 XCON: Low MDB USERS Registry Entry Causes Slow Connector

Additional query words: delivery restrictions

Keywords: kbprb KB263924

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