SPF, which abbreviates Sender Policy Framework, is a verification system that is aimed at stopping the so-called e-mail forging. In simple terms, this means sending a message from one email and making it appear to be sent from another with the idea to scam in some manner the person opening it. If the SPF protection is running for a domain name, a record which has all the mail servers authorized to email messages with addresses within the domain is created. The record is kept on all of the DNS servers that route the web traffic around the world, so that they all can identify if an e-mail message originates from a valid server or not. The verification is done at the very first server where the e-mail goes through and in the first case the email message is forwarded, and in the second one it's removed and it never gets to the intended recipient. Using SPF records for your domain names will prevent any unauthorized people from using your emails for malicious objectives.