SPF, which is an abbreviation for Sender Policy Framework, is a validation system that aims at preventing the so-called e-mail counterfeiting. Essentially, this indicates sending a message from one e-mail and making it seem to be sent from another one with the idea to scam in some manner the individual receiving it. In the event that the SPF protection is active for a domain, a record that contains all of the mail servers authorized to email messages with addresses within the domain is made. The record is saved on all DNS servers that direct the Internet traffic across the globe, so that they all will recognize if an e-mail message comes from an authentic server or not. The verification is done at the very first server where the e-mail goes through and in the first case the message is forwarded, whereas in the second one it's discarded and it never gets to the supposed recipient. Applying SPF records for your domain names will prevent all unwanted people from making use of your emails for harmful purposes.