SPF, which is an abbreviation for Sender Policy Framework, is a certification system that is aimed at protecting against the so-called e-mail faking. Essentially, this indicates sending some message from one email and making it seem to be sent from a different one with the objective to scam in some manner the individual getting it. In the event that the SPF protection is active for a domain name, a record which has all the mail servers authorized to email messages with addresses part of the domain is created. The record is kept on all the DNS servers that direct the web traffic globally, therefore they all can recognize if an e-mail message comes from a legitimate server or not. The check is conducted at the first server where the email goes through and in the first case the message is forwarded, and in the second it is removed and it never gets to the supposed recipient. Applying SPF records for your domains will prevent any unwanted people from making use of your email addresses for harmful purposes.