SPF, which is an abbreviation for Sender Policy Framework, is a verification system that aims at blocking the so-called email forging. Basically, it indicates sending a message from one email address and making it appear to be sent from another with the objective to scam in some way the person opening it. In case the SPF protection is activated for a domain, a record which contains all the mail servers authorized to send messages with addresses under the domain is created. The record is stored on all of the DNS servers that route the web traffic across the globe, thus they all can recognize if an e-mail message comes from a trustworthy server or not. The check is conducted 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 it's discarded and it never reaches the intended recipient. Employing SPF records for your domains will prevent all unauthorized people from using your email addresses for harmful purposes.
