Unable to Authenticate iTunes desktop application through the ProxySG. 

In the iTunes application, when trying to authorize an account, the user cannot send the username/passord through the ProxySG.

Suggestions in the below Symantec KB articles were followed and did not produce a successful result:

166560

165359

166793

165911

Also, tried allowing domains from this Apple article, which was not successful:

Add this to the Content Policy Language (CPL) Local file or to a CPL Layer in the Visual Policy Manager (VPM):

<Proxy>
request.header.User-Agent="iTunes" authenticate(no) detect_protocol(none) allow

The CPL code above matches on traffic coming from iTunes, proxy does not require the traffic to be authenticated, and proxy will not attempt to recognize the protocol to send for further inspection.