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Q159184: XADM: No Messages from MTA with High Directory Service Activity

Article: Q159184
Product(s): Microsoft Exchange
Version(s): winnt:4.0
Operating System(s): 
Keyword(s): exc4
Last Modified: 11-JUN-2002

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The information in this article applies to:

- Microsoft Exchange Server, version 4.0 
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IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

  Q256986 Description of the Microsoft Windows Registry

SYMPTOMS
========

You may have difficulty delivering messages with the Microsoft Exchange Server
message transfer agent (MTA). The symptoms for this problem are as follows:

- The directory service is consistently very busy (processor use is 20 percent
  or greater).

- MTA processor usage is quite low.

- The MTA work queue consistently has a backlog of messages.

- Messages are not delivered to the server.

- The global address list is very large (20,000 users or more).

CAUSE
=====

This problem is caused by time consuming fuzzy proxy directory service searches
on large global address lists.

RESOLUTION
==========

Apply the fix mentioned in the "Status" section of this article. If this fix
does not correct the problem, perform one of the following steps:

- Create the "Allow fuzzy proxy search" registry value and set it to 0. To do
  this, you need to edit the registry.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems
that may require you to reinstall your operating system. Microsoft cannot
guarantee that you can solve problems that result from using Registry Editor
incorrectly. Use Registry Editor at your own risk.

  1. Start Registry Editor (Regedt32.exe).

  2. Under the HKEY_LOCAL_MACHINE subtree, go to the following subkey:

  SYSTEM\CurrentControlSet\Services\MSExchangeMTA\Parameters

  3. Define the following registry value:

  Allow fuzzy proxy search

     Set this value to 0. This case-sensitive registry value is a DWORD value
     type. If you set the "Allow fuzzy proxy search" value to 0, you disable
     the fuzzy proxy search. If this registry value does not exist, the MTA
     assumes that this setting has a value of 1, and enables fuzzy proxy
     searches.

  4. Quit Registry Editor.

- If the problem persists, disable the alternate recipient Redirect and Deliver
  option for every mailbox on the server. To do this, in each mailbox, click
  the Delivery Options tab, and under Alternate Recipient, click None.

STATUS
======

Microsoft has confirmed this to be a problem in Microsoft Exchange Server,
version 4.0. This problem was corrected in the latest Microsoft Exchange 4.0
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

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

This behavior may occur if the MTA attempts to deliver a message addressed to an
X.400 proxy that does not exactly match an address in the global address list,
and the proxy contains a substring that is similar to other addresses in the
global address list. For example, message delivery may be slow if a message is
addressed to an X.400 proxy that is similar to the following:

  X400:C=US;A= ;P=Microsoft;CN=PaulBon

This address does not fully match the defined X.400 address for that mailbox. The
MTA makes a request for the DS to resolve the address if there are thousands of
other X.400 proxies in the global address list that contain the following
substring:

  X400:C=US;A= ;P=Microsoft

If the directory service is unable to resolve the full address by means of an
exact match, the directory service attempts to perform a fuzzy proxy search
based on the parsed substrings.

By default, the MTA attempts to perform a fuzzy proxy search if it is unable to
match the O/R address when it performs a DS_Search. To disable the fuzzy proxy
search, add the "Allow fuzzy proxy search" registry value and set it to 0.

For additional information about the fuzzy proxy search in Microsoft Exchange
Server versions 5.0 and 5.5, click the article number below to view the article
in the Microsoft Knowledge Base:

  Q176046 XCON: Routing Issues with Microsoft Exchange Server, Version 5.0


Additional query words: DS

======================================================================
Keywords          : exc4 
Technology        : kbExchangeSearch kbExchange400 kbZNotKeyword2
Version           : winnt:4.0
Issue type        : kbbug
Solution Type     : kbfix

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