Microsoft KB Archive/177006

= XADM: MTA May Fail During Mailstorms Involving Large DLs =

Article ID: 177006

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 Q177006





SYMPTOMS
If a brief, intense flurry of messages and replies (also known as a mailstorm) occurs in an Exchange Server organization and involves one or more very large distribution lists (DLs), the Microsoft Exchange message transfer agent (MTA) may fail repeatedly. The Event Log will typically show events 2051 and 9405 for the MTA preceding the failures, and the exceptions generated will usually all have the same error code, 0xe0050803.



MORE INFORMATION
Under certain conditions, a message sent to a very large DL may generate a large volume of replies and replies-to-replies over a short period, all addressed to the same DL. This can cause a mailstorm that increases the load on messaging servers exponentially over a period of minutes or hours. Under these high-stress conditions, occasional failures of the MTA as described in this article may occur.



WORKAROUND
Temporarily or permanently place delivery restrictions on the distribution list(s) involved in the mailstorm, to prevent the message traffic from escalating as multiple users reply to messages sent to the lists. When the traffic drops, the MTAs will stop failing. Under extreme conditions, it may be necessary to delete the MTA queues or take other urgent action to reduce traffic.



STATUS
Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 5.0. This problem has been corrected in the latest Microsoft Exchange Server 5.0 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: volume alias traffic storm

Keywords: kbbug kbfix KB177006

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