Err Msg: HTTP/1.1 407 Proxy Authentication Required

ID: Q222561

The information in this article applies to:


When you attempt to use the following syntax to pass FTP logon information from Internet Explorer 4.x through Microsoft Proxy Server 2.0, you are prompted for domain credentials three times.
The operation fails after the third prompt for domain credentials, and the following error message occurs:
407 Proxy Authentication Required
You must authenticate with a proxy server before this request can be serviced.
Please logon to your proxy server and then try again.


Internet Explorer passes the username and password from the URL as the proxy authentication credentials.


A supported fix that corrects this problem is now available from Microsoft, but it has not been fully regression tested and should be applied only to systems experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:
The English version of this fix should have the following file attributes or later:
Version File name
4.72.3513.1101 Wininet.dll

NOTE: If this product was already installed on your computer when you purchased it from the Original Equipment Manufacturer (OEM) and you need this fix, please call the Pay Per Incident number listed on the above Web site. If you contact Microsoft to obtain this fix, and if it is determined that you only require the fix you requested, no fee will be charged. However, if you request additional technical support, and if your no-charge technical support period has expired, or if you are not eligible for standard no-charge technical support, you may be charged a non-refundable fee.

For more information about eligibility for no-charge technical support, see the following article in the Microsoft Knowledge Base:
Q154871 Determining If You Are Eligible for No-Charge Technical Support


You can also use one of the following workarounds to resolve this issue:


Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article.

Additional query words:

Keywords          : 
Version           : WINDOWS:3.02,4.0,4.01,4.01 Service Pack 1,4.01 Service Pack 2; winnt:2.0
Platform          : WINDOWS winnt 
Issue type        : kbbug 

Last Reviewed: July 9, 1999