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Q184542: XFOR: Internet Mail Service Very Slow with High Message Volume

Article: Q184542
Product(s): Microsoft Exchange
Version(s): winnt:5.0,5.5
Operating System(s): 
Keyword(s): 
Last Modified: 08-MAR-2000

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The information in this article applies to:

- Microsoft Exchange Server, versions 5.0, 5.5 
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SYMPTOMS
========

You may experience either of the following symptoms:

- When an extremely large number of Simple Mail Transfer Protocol (SMTP)
  messages are sent through the Internet Mail Service and the Internet Mail
  Service is unable to resolve some of the Domain Name System (DNS) addresses
  associated with the messages, the Internet Mail Service may take a long time
  to send the messages.

  -OR-

- When the outbound Internet Mail Service message queue contains a large number
  of messages, the Internet Mail Service may take an unusually long time to
  start.

CAUSE
=====

These problems can occur for the following reasons:

- The rate at which the Internet Mail Service delivers SMTP messages is limited
  in part by the number of resolver threads and SMTP worker threads that are
  available. If message volume is very high and DNS name resolution is
  frequently unsuccessful, the number of available threads can become very low.

- When you start the Internet Mail Service, it processes the destination domain
  list. The method by which it processes the destination domain list can be
  inefficient, particularly when the outbound message queue contains a large
  number of messages.

WORKAROUND
==========

You can increase the number of resolver threads and SMTP worker threads that are
available when the Internet Mail Service starts, but only by increasing the
value assigned to the ThreadsPerProcessor variable.

STATUS
======

Microsoft has confirmed this to be a problem in Microsoft Exchange Server
version 5.0.


A supported fix is now available, but has not been fully regression-tested and
should be applied only to systems experiencing this specific problem. Unless you
are severely impacted by this specific problem, Microsoft recommends that you
wait for the next service pack that contains this fix. Contact Microsoft
Technical Support for more information.

This fix has been posted to the following Internet location:

  ftp://ftp.microsoft.com/bussys/exchange/exchange-public/fixes/Eng/Exchg5.0/Post-SP2-IMS/




Microsoft has confirmed this to be a problem in Microsoft Exchange Server version
5.5. This problem has been corrected in the latest U.S. service pack for
Microsoft Exchange Server version 5.5. 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


MORE INFORMATION
================

After you apply the fix, three new registry values are available under the
following registry key:

  HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIMC
  \Parameters

NOTE: The above registry key is one path; it has been wrapped for readability.

The following registry values are available:

  Value Name            Value Type   Description
  -----------------------------------------------------------------------
  SMTPWorkerThreads     REG_DWORD    If this registry value exists, it
                                     represents the number of SMTP worker
                                     threads that are available when the
                                     Internet Mail Service starts.

  ResolverThreads       REG_DWORD    If this registry value exists, it
                                     represents the number of resolver
                                     threads that are available when the
                                     Internet Mail Service starts.

  DestinationDomain-    REG_DWORD    If this registry value exists, it
  Threshold                          represents the number of
                                     DestinationDomain objects that are
                                     cached before the Internet Mail
                                     Service attempts to reduce the size
                                     of the destination domain list.


Additional query words: ims internet mail connector imc

======================================================================
Keywords          :  
Technology        : kbExchangeSearch kbExchange500 kbExchange550 kbZNotKeyword2
Version           : winnt:5.0,5.5
Issue type        : kbbug
Solution Type     : kbfix

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