SPF, which is an abbreviation for Sender Policy Framework, is an authentication system that is aimed at preventing the so-called email forging. Essentially, it indicates sending some message from one e-mail address and making it appear to be sent from another with the idea 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 mail servers authorized to email messages with addresses part of the domain is generated. The record is saved on all of the DNS servers that direct the web traffic across the globe, thus they all will identify if an e-mail message originates from an authentic server or not. The verification is performed at the very first server where the e-mail goes through and in the first case the message is forwarded, while in the second it's discarded and it never gets to the supposed recipient. Employing SPF records for your domains will prevent any unwanted people from using your email addresses for harmful purposes.