Microsoft KB Archive/920856

= Error message when Exchange Server 2003 tries to retrieve compressed content in an ISA 2004 organization: &quot;The request is not supported&quot; =

Article ID: 920856

Article Last Modified on 12/4/2007

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APPLIES TO

 Microsoft Exchange Server 2003 Enterprise Edition Microsoft Exchange Server 2003 Standard Edition, when used with:  Microsoft Internet Security and Acceleration Server 2004 Enterprise Edition

 Microsoft Internet Security and Acceleration Server 2004 Standard Edition 

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SYMPTOMS
When Microsoft Exchange Server 2003 tries to retrieve compressed content in a Microsoft Internet Security and Acceleration (ISA) Server 2004 organization, you may receive the following error message:

Error Code: 500 Internal Server Error. The request is not supported.

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CAUSE
This issue may occur when either of the following conditions is true:
 * You receive compressed content through an ISA Server 2004 Web publishing rule or server publishing rule.
 * You try to download .zip file attachments from a Microsoft Outlook Web Access Web site that is published in ISA Server 2004.

ISA Server 2004 does not accept encoded or compressed content when a &quot;Publish a Web Server&quot; rule is used. By default, this rule instructs ISA Server 2004 to delete all &quot;Accept-Encoding&quot; headers from requests that are sent to the Web server. The Web server can still send a compressed response. However, the ISA Server computer does not forward the response to the client. Therefore, the client computer receives the error message.

When a mail server publishing rule is used, the rule enables the ISA Server computer to forward &quot;Accept-Encoding&quot; headers from clients to a Web server. If a client sends an &quot;Accept-Encoding&quot; header that states that the client will accept compressed content, the published Web server may send a compressed response. This is indicated by the response's &quot;Content-Encoding&quot; header. This header is accepted by the ISA Server computer and then forwarded to the client.

Note The ISA Server computer does not cache the compressed content.

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RESOLUTION
To resolve this issue, delete the current Web server publishing rule for the site. Then, run the Publish a Mail Server wizard by using the Outlook Web Access option.

To delete a Web server publishing rule in ISA Server 2004, follow these steps:
 * 1) Start the ISA Server Management snap-in.
 * 2) In the navigation tree in the left pane, click Firewall Policy.
 * 3) Under Firewall Policy, right-click the policy that you want to delete, and then click Delete.
 * 4) Click Yes, click Apply, and then click OK.

To run the Publish a Mail Server wizard by using the Outlook Web Access option, follow these steps:
 * 1) Start the ISA Server Management snap-in.
 * 2) In the right pane, click the Tasks tab, and then click Publish a Mail Server under Firewall Policy Tasks
 * 3) On the Select access type page, click Web client access: Outlook Web Access (OWA), Outlook Mobile Access, Exchange Server ActiveSync, and then click Next.
 * 4) On the Select services page, click to select the Outlook Web Access check box, and then click Next.
 * 5) On the pages that follow, follow the instructions to complete the Publish a Mail Server wizard.

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MORE INFORMATION
For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base:

837865 You receive a &quot;The request was rejected by the HTTP Security filter&quot; error message when you try to open a message from an Exchange Server that is published in ISA Server 2004

896367 Windows Server 2003 Service Pack 1 application compatibility

Keywords: kbtshoot kbprb KB920856

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