When you use a Outlook Web Access client to access an Exchange Server 2003 computer, you may receive an "HTTP 403.4" error message

When you use a Microsoft Outlook Web Access client computer to access a Microsoft Exchange Server 2003 computer that is configure for Forms Based Authentication (FBA), you may receive the following error message:

This problem occurs if the OWA client accesses the Exchange 2003 computer through a third-party firewall server. For example, you use the following URL: The SSL hardware accelerator that is installed in the third-party firewall decrypts the request and then passes the following URL to the Exchange 2003 computer: Then, Exchange 2003 returns the following URL to the OWA client: When the OWA client uses this URL to log on to the Exchange 2003 computer, you receive an "HTTP Error 403.4" error message.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

Hotfix information

The hotfix for Exchange 2003 without Service Pack 1

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.

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.

The hotfix for Exchange 2003 Service Pack 1

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.

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.You must create the SSLOffloaded registry entry for both hotfixes to work. To do this, follow these steps:

1. Click Start, click Run, type regedt32.exe, and then click OK.
2. Locate, and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\ Services\MSExchangeWeb\OWA
3. On the Edit menu, point to New, and then click DWORD Value.
4. Type SSLOffloaded for the name of the new registry entry.
5. Right-click SSLOffloaded, and then click Modify.
6. Type 1 in the Value Data box, click Decimal, and then click OK.
7. Close Registry Editor.

If you are using front-end servers and back-end servers, you only have to add this registry entry to the front-end server. If you are using only back-end servers, you have to add this registry entry to the back-end server.

To work around this problem, manually change the URL. To do this, type https://myserver/exchange/ in the Address bar in Microsoft Internet Explorer.

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

If you monitor the traffic that is captured between the third-party firewall and the Exchange 2003 computer, you notice a frame that is sent from the Exchange 2003 computer to the third-party firewall. This frame contains the following information about the location of the logon.asp page: Note This problem does not occur if Exchange 2003 is configured with Microsoft Internet Security and Acceleration (ISA) Server 2000 or with Microsoft Internet Security and Acceleration Server 2004. ISA Server can send a corrected URL back to the OWA client.

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