Microsoft KB Archive/152165

= XCON: IMS Queues Back Up to Hosts with Multiple MX Records =

Article ID: 152165

Article Last Modified on 10/28/2006

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APPLIES TO


 * Microsoft Exchange Server 5.0 Standard Edition

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This article was previously published under Q152165



SYMPTOMS
If you are running Microsoft Exchange Server 5.0 with the Internet Mail Service (IMS) installed, your server may experience slow delivery to hosts that have multiple MX records of equal weight. Internet hosts supporting multiple IP addresses are often the same hosts receiving high volumes of mail.



CAUSE
When host addresses are resolved by Domain Name Service (DNS), a list of records is returned if the site has multiple MX records defined. The IMS attempts to randomize its choice of the available MX records. This is done to spread the load evenly over the sites' MX hosts. The randomization code is behaves poorly for sites with more than a few MX records of equal weight.



STATUS
Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 5.0. This problem was corrected in the latest Microsoft Exchange 5.0 Server U.S. 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

Additional query words: america online aol.com

Keywords: kbusage KB152165

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