Mail delivery is slow in Exchange 2000 when the primary DNS server is not available

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Article ID: 829722 - View products that this article applies to.
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In Microsoft Exchange 2000 Server, message delivery to external recipients may be slower than expected when the primary DNS server is not available.


Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, submit a request to Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:
Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

File information

The English version of this hotfix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.
   Date         Time   Version            Size    File name
   19-Jun-2003  20:05  5.0.2195.6654     322,320  Aqueue.dll       
   19-Jun-2003  20:05  5.0.2195.6666      67,344  Mailmsg.dll      
   19-Jun-2003  20:05  5.0.2195.6662      38,672  Ntfsdrv.dll      
   18-May-2004  16:46  5.0.2195.6920     445,200  Smtpsvc.dll      

More information

By using Microsoft Network Monitor, you can determine the cause of the slower-than-expected mail delivery. You may find that mail delivery performance is affected by DNS query responses, as in the following situation:
  1. An initial query is made to the DNS server that is unavailable four seconds after Exchange 2000 sends the message.
  2. The query times out after three seconds, and then an additional query is made to the same server.
  3. The second query times out after six seconds, and then another query is made to the same server.
  4. This final query times out after 12 seconds. Exchange 2000 then forwards the request to the secondary DNS server. The secondary DNS server returns the response, and the message is delivered.
This process takes 25 seconds. Because the DNS responses are not cached, the whole process is repeated for each message that is sent through Exchange 2000. Therefore, mail delivery to external recipients is slower than expected.


Microsoft has confirmed that this is a bug in Exchange 2000.


Article ID: 829722 - Last Review: October 26, 2013 - Revision: 3.0
Applies to
  • Microsoft Exchange 2000 Server Standard Edition
kbnosurvey kbarchive kbautohotfix kbhotfixserver kbqfe kbinfo KB829722

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