http-status-code-407

I'm trying to get Fiddler to work with my company's proxy. Every external request is returning 407. So far I've tried adding oSession.oRequest["Proxy-Authorization"] = "YOURCREDENTIALS"; to the customized rules where I used my USERNAME:PASSWORD in base64. Still no luck. Any ideas? Thanks. mono68 Note: There is an answer with a higher voting available. Because of SO sorting it is below the accepted answer. I had the same problem, too, and solved it like this: Started Fiddler with it's standard configuration. Started IE and made a HTTP-request to an external web-site. The proxy authorization

I am working with a proxy that requires authentication, i.e., in a browser if I try to open a page it will immediately ask for credentials. I supplied same credentials in my program but it fails with HTTP 407 error. Here is my code: HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL); IWebProxy proxy = WebRequest.GetSystemWebProxy(); CredentialCache cc = new CredentialCache(); NetworkCredential nc = new NetworkCredential(); nc.UserName = "userName"; nc.Password = "password"; nc.Domain = "mydomain"; cc.Add("http://20.154.23.100", 8888, "Basic", nc); proxy.Credentials = cc; //proxy