SPF, which is an abbreviation for Sender Policy Framework, is a verification system that aims at stopping the so-called e-mail forging. In simple terms, this means sending some message from one email and making it seem to be sent from another one with the objective to scam in some way the person opening it. In the event that the SPF protection is running for a domain name, a record which contains all mail servers authorized to send messages with addresses under the domain is made. The record is placed on all the DNS servers that direct the web traffic worldwide, thus they all will identify if an e-mail message originates from a legitimate server or not. The verification is conducted at the first server where the e-mail goes through and in the first case the e-mail message is forwarded, whereas in the second one it's removed and it never reaches the supposed recipient. Applying SPF records for your domains will stop all unwanted people from using your email addresses for harmful objectives.