SPF, which is an abbreviation for Sender Policy Framework, is a verification system that aims at protecting against the so-called email forging. Essentially, this indicates sending a message from one email address and making it appear to be sent from another one with the idea to scam in some manner the individual opening it. In case the SPF protection is active for a domain, a record that contains all of the mail servers authorized to send messages with addresses in the domain is created. The record is saved on all of the DNS servers that route the Internet traffic across the globe, thus they all can recognize whether an e-mail message comes from an authentic server or not. The check is conducted at the first server where the e-mail goes through and in the first case the email message is forwarded, but in the second it is discarded and it never reaches its intended recipient. Applying SPF records for your domains will prevent all unauthorized people from using your emails for harmful purposes.