Single SMTP server with a single IP address directly connected to Internet

In this configuration the SPAM Filter gateway is installed on the same server as your SMTP software. The server only has one IP address available, SPAM Filter will need to be configured to listen on port 25 so it can accept email traffic. Your SMTP software will need to be reconfigured to listen on a different port, for example port 26. SPAM Filter will then forward clean emails to your SMTP server on port 26.All your email clients will need to be reconfigured so that their "Outgoing SMTP server" now points to your SMTP server on port 26. Alternatively, you may choose to let your email clients relay thru SPAMFilter. Please note that in order to do so, you will need to configure IP whitelists in SPAM Filter to specify the IPs from which your clients can relay from (note - there are no changes needed to clients if they connect to an Exchange server).