I have an Exchange 2010 email server running and I just changed it public IP and we are getting blocked by junk mail filters. This has happened once before but changeing the public IP back to what it was fixed the issue. This is not an option this time.
My question is how do I prevent my server being used as an open proxy? I do not allow my users to connect to there work email from home, the server is behind a router and you can not remote to the server from outside the company.