To implement our SPAM Filter server with minimal impact you would do the following.Configure SPAM Filter to listen on a different IP, for example on mail2.domain.com. This can be done by installing SPAMFilter either on a separate separate server or the same server provided it has multiple IP addresses assigned to it.Reconfigure the MX record to point to mail2.domain.com.Your SPAM Filter server will now be receiving all internet email and will then forward legitimate emails to your SMTP server at mail.domain.com. Your existing customers still have mail.domain.com for SMTP server in their email client configuration, nothing will have changed for them.