Question : Yahoo Messenger

At office, I can use Internet through Proxy Server at Port 80. I want to set up Yahoo Messenger.
How can I configure Yahoo Messenger behind firewall? How can I get port Administrator opened? May we have the way to scan port open on Proxy Server?
Thanks

Answer : Yahoo Messenger

We can close the question, I have found a sollution that is  check  option" Use HTTP 1.1 through proxy connection" in Tools >Intenet Option > Advanced tab. So, I want to get a refund.
FYI,