DOCUMENT:Q152165  27-MAR-1999  [exchange]
TITLE   :XCON: IMS Queues Back Up to Hosts with Multiple MX Records
PRODUCT :Microsoft Exchange
PROD/VER:winnt:5.0
OPER/SYS:
KEYWORDS:kbusage

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The information in this article applies to:

 - Microsoft Exchange Server, version 5.0 
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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

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Keywords          : kbusage 
Technology        : kbExchangeSearch kbExchange500 kbZNotKeyword2
Version           : winnt:5.0

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