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Q263924: Message Transfer Agent Slows Down and CPU Usage Increases

Article: Q263924
Product(s): Microsoft Exchange
Version(s): winnt:5.5
Operating System(s): 
Keyword(s): exc55
Last Modified: 06-AUG-2002

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The information in this article applies to:

- Microsoft Exchange Server, version 5.5 
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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 <MDB Users> 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:

  Q158590 XCON: Delivery Restrictions Max CPU and Slow Down Message Delivery

  Q176076 XCON: Low MDB USERS Registry Entry Causes Slow Connector


Additional query words: delivery restrictions

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Keywords          : exc55 
Technology        : kbExchangeSearch kbExchange550 kbZNotKeyword2
Version           : winnt:5.5
Issue type        : kbprb

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