SPF, which abbreviates Sender Policy Framework, is an authentication system that aims at preventing the so-called e-mail faking. In simple terms, this indicates sending a message from one e-mail address and making it appear to be sent from another with the purpose to scam in some manner the individual opening it. In the event that the SPF protection is active for a domain name, a record which has all the mail servers authorized to send messages with addresses part of the domain is generated. The record is placed on all the DNS servers that route the Internet traffic internationally, therefore they all will recognize if an email message originates from an authentic server or not. The verification is done at the first server where the e-mail goes through and in the first case the email message is forwarded, and in the second one it is removed and it never gets to the intended recipient. Applying SPF records for your domain names will prevent all unwanted people from making use of your email addresses for harmful purposes.