Hello!
That website translated in unicode is the equivalent of:
3 "w"DOTxn--espaaescultura-tnbDOTes
So if you insert that one in the HTTP Proxy it should be accepted

Regards,
Daniele
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Thanks a lot for this very simple and efficient workaround solution to my problem.
Here is an URL which helps to perform any Unicode conversion for EFW: 3 "w"DOTnameDOTcom/punycode-converter
Regards