Question about open proxy

I am trying to close my company's open proxy to prevent abuse by spammers. 
We think it is now closed, but can you tell me the best way to test this?  
Your site showed up in a metacrawler search for "open proxy" but I'm not sure 
what your products do. 
Thanks for any help you can provide.
Dave Owen
President
DHY Corp
Lakeville, MN
952-469-1000 office
612-867-0438 cell
dowen-E11xN4IjFaRBDgjK7y7TUQ@xxxxxxxxxxxxxxxx
dhydeo-YDxpq3io04c@xxxxxxxxxxxxxxxx