You configure Kerberos authentication between the front-end and back-end servers that are running Microsoft Exchange Server 2003. In this configuration, the following event is logged in the Application log on the front-end server:

Event Type: Warning
Event Source: EXPROX
Event Category: None
Event ID: 1000
Date: Date
Time: Time
User: N/A
Computer: Front-end_Server_Name
Description: Microsoft Exchange Server has detected that NTLM-based authentication is presently being used between this server and server 'Back-end_Server_Name'. NTLM is still a secure authentication mechanism and protects users' credentials. However, this indicates that there may be a configuration issue preventing the use of Kerberos authentication. If this condition persists, please verify that both this server and server 'Back-end_Server_Name' are properly configured to use Kerberos authentication. After applying any changes it may be necessary to restart Internet Information Services on both the front-end and back-end servers. As a result the authentication protocol fails back to NTLM.

This event indicates that NTLM authentication is being used instead of Kerberos authentication between the front-end and the back-end servers.

For more information about Event ID 1000, visit the Microsoft Events and Errors Message Center (EEMC) at the following Microsoft Web site:

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This problem occurs when you use a disjointed DNS namespace. For example, in a domain that is named "country.domain.com," you use a fully-qualified domain name (FQDN) for the front-end server that resembles the following name: In this case, a request is made for a Kerberos Ticket in the domain "Region1.country.domain.com." However, this domain does not exist.

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Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

After you install this hotfix, add the following registry key:Note 0 and 1 are the only valid values. 0 is off, 1 is on.

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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. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

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, contact 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.

Prerequisites

You must install Microsoft Exchange Server 2003 Service Pack 2 (SP2) before you apply the hotfix.
For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Restart requirement

You do not have to restart the computer after you apply the hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The global version of this hotfix has the file attributes (or later file attributes) 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 item in Control Panel.

File name	File version	File size	Date	Time	Platform
Exprox.dll	6.5.7651.19	415,232	22-Apr-2006	05:01	x86

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Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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For more information about the terminology that Microsoft uses for software that is corrected after it is released, click the following article number to view the article in the Microsoft Knowledge Base: For more information about the naming schema for Exchange software updates, click the following article number to view the article in the Microsoft Knowledge Base:

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