Error message when you access Outlook Web Access through ISA Server 2004: "Error Code: 500 Internal Server Error. The data area passed to a system call is too small."

When you access Microsoft Office Outlook Web Access through Microsoft Internet Security and Acceleration (ISA) Server 2004, you receive an error message that resembles the following:This problem occurs if the following conditions are true:

• You are using the forms-based authentication filter in ISA Server 2004.
• You have installed a third-party add-in program for Microsoft Exchange.

This problem occurs when the response from the Exchange server that provides Outlook Web Access services contains the following HTTP header:

To resolve this problem, install hotfix 925232. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

This hotfix makes ISA Server ignore the "Expires" header when a "Cache-Control: no-cache" header is included in the response from the Exchange server. Both headers are used to prevent the caching of HTTP content and can be used together.

If the third-party add-in for Exchange uses only the "-1" value in the "Expires" header, you must enable the add-in program to also include the "Cache-Control: no cache" header. To do this, see the third-party add-in program's documentation, or contact the manufacturer of the add-in program.

For information about your hardware manufacturer, visit the following Web site: Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.

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

The forms-based authentication filter in ISA 2004 is tested for an Outlook Web Access scenario that does not include any add-in programs. In this scenario, Outlook Web Access does not pass the "-1" value for the "Expires" header. Therefore, access to Outlook Web Access is successful. The forms-based authentication filter for Outlook Web Access in ISA Server 2004 supports the following formats for the "Expires" header:

• Sun, 06 Nov 1994 08:49:37 GMT
• Sunday, 06-Nov-94 08:49:37 GMT
• Sun Nov 6 08:49:37 1994