You cannot update scan engines through a proxy on a computer that is running Forefront Security for Exchange Server

You have a computer that is running Microsoft Forefront Security for Exchange Server Service Pack 1. You try to update the scan engines through a proxy that is configured for NTLM. However, Forefront does not send credentials to answer to the NTLM challenge. Therefore, the scan engine updates are not successful. Additionally, the following error message is logged in the WinHTTP log:

To resolve this problem, you must install Hotfix Rollup 3 for Microsoft Forefront Security for Exchange Server Service Pack 1.
For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Note Microsoft Forefront Security for Exchange Server Service Pack 1 must be installed before you install Hotfix Rollup 3 for Microsoft Forefront Security for Exchange Server Service Pack 1.

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

To download Microsoft Forefront Security for Exchange Server Service Pack 1, visit the following Microsoft Download Center Web site: For more information about Forefront Security for Exchange Server, visit the following Microsoft Web site: