SPF, which abbreviates Sender Policy Framework, is a verification system that is aimed at preventing the so-called email counterfeiting. In simple terms, it indicates sending some message from one email address and making it seem to be sent from another with the objective to scam in some manner the individual opening it. If the SPF protection is running for a domain name, a record that contains all of the mail servers authorized to send messages with addresses under the domain is made. The record is saved on all DNS servers that route the web traffic around the world, therefore they all will identify if an email message originates from a legitimate server or not. The check is performed at the first server where the e-mail goes through and in the first case the e-mail message is forwarded, but in the second it's removed and it never gets to its intended recipient. Applying SPF records for your domain names will prevent any unauthorized people from using your email addresses for harmful objectives.