SPF, which abbreviates Sender Policy Framework, is an authentication system that is aimed at blocking the so-called e-mail faking. Essentially, this means sending a message from one e-mail address and making it seem to be sent from a different one with the idea to scam in some manner the individual receiving it. If the SPF protection is running for a domain, a record which contains all mail servers authorized to send messages with addresses in the domain is generated. The record is stored on all of the DNS servers that direct the web traffic worldwide, so that they all will recognize if an email message originates from an authentic server or not. The check is performed at the very first server where the e-mail goes through and in the first case the message is forwarded, and in the second one it is removed and it never reaches the supposed recipient. Applying SPF records for your domains will stop any unwanted people from making use of your emails for harmful purposes.