DOCUMENT:Q263924 06-AUG-2002 [exchange] TITLE :Message Transfer Agent Slows Down and CPU Usage Increases PRODUCT :Microsoft Exchange PROD/VER:winnt:5.5 OPER/SYS: KEYWORDS:exc55 ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Exchange Server, version 5.5 ------------------------------------------------------------------------------- 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: 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 ====================================================================== Keywords : exc55 Technology : kbExchangeSearch kbExchange550 kbZNotKeyword2 Version : winnt:5.5 Issue type : kbprb ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2002.