SPF, which abbreviates Sender Policy Framework, is a verification system that aims at stopping the so-called e-mail faking. In simple terms, this indicates sending a message from one email and making it seem to be sent from another one with the purpose to scam in some manner the individual getting it. When the SPF protection is active for a domain, a record which contains all the mail servers authorized to send messages with addresses under the domain is generated. The record is stored on all the DNS servers that direct the web traffic internationally, so they all can recognize if an email message comes from a valid server or not. The verification is conducted at the very first server where the email goes through and in the first case the message is forwarded, but in the second one it's removed and it never gets to the supposed recipient. Using SPF records for your domains will prevent all unwanted people from using your email addresses for malicious objectives.