Microsoft KB Archive/223385

= XIMS: IMS Routing Incorrectly When Directory Replication Is Enabled =

Article ID: 223385

Article Last Modified on 10/26/2006

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APPLIES TO


 * Microsoft Exchange Server 5.5 Standard Edition

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This article was previously published under Q223385



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:

256986 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, click the following article number to view the article in the Microsoft Knowledge Base:

191014 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

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.  Stop the Exchange Server Internet Mail Service. Apply the fixed files noted above. Start Registry Editor (Regedt32.exe). Go to the following location in the registry:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIMC\Parameters

 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).

 Click OK, and quit Registry Editor.</li> Restart the Microsoft Exchange Internet Mail Service.</li></ol>

<div class="status_section">

STATUS
Microsoft has confirmed that this is a problem in Microsoft Exchange Server version 5.5. This problem was first corrected in Exchange Server 5.5 Service Pack 3.

Keywords: kbbug kbfix kbqfe KB223385

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