Specifying proxy server in web.config

Hi all,
 I am getting a The remote server returned an error: (407) Proxy Authentication Required. error from a call to the web, and I believe I need to put the details of my proxy server into my web.config file.
 
I've tried to do this by the following but to no avail, how am I doing it wrong please?
 
 
<defaultProxy> <proxy proxyaddress ="http://contoso:8080" bypassonlocal="True" usesystemdefault="False" /> </defaultProxy> 
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