We run a Small Business Server box and it primarily provides our email via Exchange Server 2003.
Recently, our ISP indicated that our server was relaying or forwarding spam messages. I have tried a number of different things to correct this, and I would like to share a few of the steps of I have taken.
On a slightly unrelated note, some nefarious characters kept trying to login to our server via Remote Desktop. I have defended against these attacks by using a program called 2x SecureRDP. This ‘filters’ incoming RDP connections and stops repetitive RDP attacks before they occure.
I hope some of this information has been useful to you.