Microsoft KB Archive/253284

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Large Number of Alias Domains Causes 550 Error for Valid Domains

Article ID: 253284

Article Last Modified on 2/28/2007


  • Microsoft Windows 2000 Advanced Server

This article was previously published under Q253284


When the Simple Mail Transport Protocol (SMTP) service is configured with a very large number of alias domains, the following error message may be returned for some of the domains:

550 5.1.7 unable to relay


This behavior occurs because SMTP uses the number of messages to control how many handles it keeps open instead of using the number of opened handles to determine if more handles need to be opened. If there are thousands of messages queued up, perhaps to a remote system that is down, other messages that could be processed must wait for redundant handle opens/closes and their corresponding flush files.


To resolve this problem, obtain the latest service pack for Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

260910 How to Obtain the Latest Windows 2000 Service Pack


Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Windows 2000 Service Pack 1.

Keywords: kbhotfixserver kbqfe kbbug kbenv kberrmsg kbfix kbwin2000sp1fix KB253284