SPF, which is an abbreviation for Sender Policy Framework, is a validation system that aims at protecting against the so-called e-mail counterfeiting. Basically, it indicates sending some message from one email address and making it appear to be sent from another one with the objective to scam in some manner the person opening it. In case the SPF protection is active for a domain, a record which has all of the mail servers authorized to send messages with addresses within the domain is generated. The record is kept on all DNS servers that direct the Internet traffic all over the world, so they all can recognize whether an e-mail message originates from a legitimate server or not. The check is done at the first server where the email goes through and in the first case the e-mail message is forwarded, whereas in the second one it is removed and it never reaches the supposed recipient. Employing SPF records for your domain names will stop all unwanted people from using your email addresses for harmful purposes.