Originally Posted by HostColor
For any reason MaxMind gives high score to orders which do not come from an IP address located close to the billing address of the credit card. Even WHMCS themselves consider this as a high fraud risk! When the users uses email address with any free email server (Gmail, Yahoo, etc.), this is considered as additional risk.
Nailed it on the head. Using free email addresses is normally a big red light, but again this depends on what service your selling (web hosting, vps, servers, etc) and who your target audience is.