Mail Exchange (“MX”) records are a resource record that specifies the mail server responsible for accepting e-mail messages on behalf of a recipient’s domain and a preference value used to prioritize mail delivery. For all the domains and websites that our users mark as important we cross reference the MX Records for those domains to see if a domain name or website that looks “safe,” “parked,” or otherwise unused, is actually registered as a base point for sending spam or to run a phishing scam.