XCLN: OWA "HTTP 403 - Forbidden" Error Message Because of Missing or Damaged Exchfilt.dll File (290989)

SYMPTOMS

When you attempt to gain access to a Microsoft Outlook Web Access (OWA) Web page, you may receive an error message that is similar to:

You are not authorized to view this page.

You might not have permission to view this directory or page using the credentials you supplied.

If you believe you should be able to view this directory or page, please try to contact the Web site by using any e-mail address or phone number that may be listed on the server_name home page.

Click Search to look for information on the Internet.

HTTP Error 403 - Forbidden
Internet Explorer

This error message may occur even though the permissions are set correctly. For additional information about how to set permissions correctly, click the article number below to view the article in the Microsoft Knowledge Base:

175892 XWEB: Permissions Required for Outlook Web Access

The permissions are set to "Execute (including script)" on the Exchange Server virtual directory.

CAUSE

Although the error message indicates that there is an incorrect default Web site, this issue occurs because the Internet Server Application Programming Interface (ISAPI) filter for Exchfilt.dll either is not loaded or is not working properly.

RESOLUTION

To resolve this issue, replace the existing Exchfilt.dll file in the drive:\Exchsrvr\Server\Setup\I386 folder with the Exchfilt.dll file from either the Exchange Server 5.5 CD-ROM or the Winnt\System32 folder. If you are running Microsoft Small Business Server (SBS) version 4.5, you can obtain the Exchfilt.dll file from either CD-ROM 3 of the SBS 4.5 CD-ROMs or the Winnt.sbs\System32 folder.