We have an Exchange 2007 server running on our 2008SBS server. External security scans indicate we have an open relay. I have verified this with several resources. I need to setup the server to only allow authenticated users to send mail. We only have one Exchange server. I have read so many posts and articles and I still don't know what I need to do. I have found some posts that recommend using the Exchange Management Shell. I don't have any experience with it. I need to make sure if I make a change that causes other problems that I know how to undo the change.
On my default receive connector I have TLS enabled. Basic authentication with offcer basic authentication only after starting TLS disabled. I also have integrated windows authentication enabled. In the permission group I have to following selected. Anoymous users, exchange users,exchange servers and legacy exchange servers.
I know that by default Exchange 2007 isn't setup to be an open relay, but something went wrong.