MSN Messenger, Provoxy, Tor

I am pretty sure that I have correctly TORified my version of MSN
Messenger using Privoxy and Tor software. At least I can make a
connection and chat to my mates with the configuration I set up.

But how can I check that the messages I now send out via Messenger are
truly anonymous until they reach the intended recipient. How can I
prove to myself that Privoxy/Tor has made any difference?

Hope someone can help me.
Thanks,
Ed

Nomen Nescio