Users receive a 401 error message when they try to access a mailbox that is in an Exchange Server 2003 front-end server by using Outlook Web Access

If a user tries to access a mailbox that is in a Microsoft Exchange Server 2003 front-end server by using Microsoft Outlook Web Access, the user receives a 401 error message.

By default, the Exprox.dll file builds the cache for the Exchange Server 2003 back-end server on the Exchange Server 2003 front-end server. The Exprox.dll file builds the cache by using the Dsaccess.dll file to provide a list of objects that has the msExchPrivateMDB attribute or the msExchPublicMDB attribute.

In a customer environment, if the values of the msExchPrivateMDB attribute are more than one thousand, the cache is incomplete. When a user tries to log on to the Exchange Server 2003 front-end server by using Outlook Web Access, the user receives a 401 error message. Additionally, the user cannot log on to the Exchange Server 2003 front-end server.

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

Because of file dependencies, this hotfix requires that Microsoft Exchange Server 2003 Service Pack 1 (SP1) be installed.

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 your computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfix.

File information

The English 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 tool in Control Panel.

To work around this problem, you can perform one of the following methods:

• Change the authentication method between the Exchange Server 2003 front-end server and the Exchange Server 2003 back-end server to basic authentication.
  For more information, click the following article number to view the article in the Microsoft Knowledge Base:
  899384  (http://support.microsoft.com/kb/899384/ ) You receive an "HTTP Error 403" error message when you try to log on to your mailbox in Outlook Web Access
• Add a public folder store to the Exchange Server 2003 back-end server.
• Increase the Lightweight Directory Access Protocol (LDAP) query page size.

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

For more information about the Microsoft Exchange Server 2003 Service Pack 2 version of this hotfix, click the following article number to view the article in the Microsoft Knowledge Base: