SPF, which abbreviates Sender Policy Framework, is a validation system that aims at preventing the so-called email faking. Essentially, this indicates sending some message from one email address and making it look like it’s 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 mail servers authorized to send messages with addresses under the domain is made. The record is stored on all of the DNS servers that direct the Internet traffic across the globe, thus they all can recognize whether an email message comes from a valid server or not. The verification is performed at the first server where the email goes through and in the first case the message is forwarded, while in the second one it's discarded and it never reaches its intended recipient. Applying SPF records for your domain names will stop any unauthorized people from using your emails for harmful purposes.