SPF, which abbreviates Sender Policy Framework, is an authentication system that aims at preventing the so-called e-mail counterfeiting. Essentially, this indicates sending some message from one e-mail address and making it seem to be sent from another one with the purpose to scam in some manner the person opening it. If the SPF protection is activated for a domain name, a record that includes all of the mail servers authorized to send messages with addresses part of the domain is made. The record is kept on all of the DNS servers that direct the web traffic internationally, so that they all can identify whether an e-mail message originates from an authentic server or not. The verification is done at the very first server where the email goes through and in the first case the email message is forwarded, and in the second one it's removed and it never reaches the intended recipient. Using SPF records for your domains will prevent any unauthorized people from making use of your emails for harmful objectives.