DOCUMENT:Q223385  11-JUN-2002  [exchange]
TITLE   :XIMS: IMS Routing Incorrectly When Directory Replication Enabled
PRODUCT :Microsoft Exchange
PROD/VER::5.5
OPER/SYS:
KEYWORDS:exc55 EXC55SP3Fix

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The information in this article applies to:

 - Microsoft Exchange Server, version 5.5 
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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
========

The Internet Mail Service may route mail incorrectly when directory replication
is enabled. Instead of going through a single hop, the mail may go through
multiple hops. The issue has to do with the way Exchange Server builds its
routing topology when directory replication is enabled.

For example, if a company has three Exchange Server Sites that do not replicate,
and the users want to send mail using SMTP, they address mail to each other as
user@site1.microsoft.com. Exchange Server looks up site1.microsoft.com in Domain
Name System (DNS), and the mail is sent directly. If those three sites begin
Exchange Server directory replication in a hub-and-spoke manner, users will gain
the benefit of being able to pick users out of the global address list, but all
mail from Site1 to Site2 will flow first through the hub by default. This adds
an additional hop to the mail flow, and also creates a single point of failure.

CAUSE
=====

When Exchange Server builds its routing table, it doesn't detect that sites are
connected by means of Internet Mail Service, and therefore, does not set routing
to direct using DNS.

RESOLUTION
==========

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.
To resolve this problem, obtain the latest service pack for Exchange Server
version 5.5. For additional information, please see the following article in the
Microsoft Knowledge Base:

   Q191014 XGEN: How to Obtain the latest Exchange Server 5.5 Service Pack

The English version of this fix should have the following file attributes or
later:

Component: Internet Mail Service

+---------------------------+
| File name    | Version    | 
+---------------------------+
| Imcmsg.dll   | 5.5.2580.0 | 
+---------------------------+
| Msexcimc.exe | 5.5.2580.0 | 
+---------------------------+

This hotfix has been posted to the following Internet location as Psp2imca.zip
and Psp2imci.zip:

   ftp://ftp.microsoft.com/bussys/exchange/exchange-public/fixes/Eng/Exchg5.5/PostSP2/imc-fix


In addition to the new files noted above, the following registry changes must be
made to enable this functionality. To make the registry changes, perform the
following steps:

NOTE: The registry change is required to enable this feature in SP3 and later
service packs.

1. Stop the Exchange Server Internet Mail Service.

2. Apply the fixed files noted above.

3. Start Registry Editor (Regedt32.exe).

4. Go to the following location in the registry:

   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIMC\Parameters

5. On the Edit menu, click Add Value, and add the following value:

   Value Name: OnlySystemMessagesUseCDs
   Data Type: REG_DWORD
   Value: 0x0, 0x1
   Default: 0x0 (not in registry by default)

After this key is set, Exchange Server will detect that sites are connected by
Internet Mail Service, and will set its routing to direct using DNS (1 hop).

6. Click OK, and quit Registry Editor.

7. Restart the Microsoft Exchange Internet Mail Service.

STATUS
======

Microsoft has confirmed this to be a problem in Microsoft Exchange Server
version 5.5. This problem was first corrected in Exchange Server 5.5 Service
Pack 3.

Additional query words:

======================================================================
Keywords          : exc55 EXC55SP3Fix 
Technology        : kbExchangeSearch kbExchange550 kbZNotKeyword2
Version           : :5.5
Issue type        : kbbug
Solution Type     : kbfix

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