Praetor may be installed on a standalone machine using Windows 2000 or XP Professional Edition,  Windows 2000 Server, or Windows 2003 .NET Server.  (Praetor WebHelp - Chapter 3)

If Praetor is placed behind a firewall, arrange to let port 25 on the firewall be redirected to the Praetor machine.

Configure the native Windows IIS SMTP Server used by Praetor to route acceptable messages to your normal Exchange, Domino or other SMTP mail server.   Then enable Praetor filtering via the supplied administrator Microsoft Management Console application.

If placed on the unprotected side of a firewall, add a new DNS MX record for the Praetor machine, specifying a preference value lower than the existing SMTP mail server.

This is critical as it puts the Praetor machine into the production email stream with no drawbacks.  In 24-48 hours, the new MX record is propagated through-out the Internet. During this transition period, Praetor will receive an increasing amount of your  email traffic.

If Praetor is disabled or the machine is taken off-line, all Internet mail servers will try to connect to Praetor first and, with no response, then connect to the original mail server.