Microsoft KB Archive/300975

= SMTP Service Stops Delivering Mail if DNS Response Fails =

Article ID: 300975

Article Last Modified on 10/22/2002

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APPLIES TO


 * Microsoft Commercial Internet System 2.0

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This article was previously published under Q300975



SYMPTOMS
Microsoft Commercial Internet System (MCIS) Simple Mail Transfer Protocol (SMTP) servers may randomly exhibit mail queueing in the Queue folder. No errors appear in system or application logs, and the threads for the service all appear to be waiting.



CAUSE
The Domain Name System (DNS) server fails to respond to a query that the SMTP service performs. As a result, the SMTP thread remains waiting for the response.



RESOLUTION
To resolve this problem, ensure that the SMTP server is always able to access the DNS server through a socket connection.



STATUS
Microsoft has confirmed that this is a problem in Commercial Internet System 2.0.



MORE INFORMATION
Microsoft Windows NT 4.0 does not cache any resolved DNS names, so the requests cannot be completed successfully if the DNS is not available through Windows sockets. Microsoft Windows 2000 does cache resolved DNS names, which reduces the need for requests.

Keywords: kbbug kbfix KB300975

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