SPF, which abbreviates Sender Policy Framework, is a verification system that is aimed at protecting against the so-called e-mail counterfeiting. Basically, this indicates sending a message from one email and making it look like it’s sent from another with the idea to scam in some manner the individual receiving it. In case the SPF protection is active for a domain, a record which has all of the mail servers authorized to send messages with addresses in the domain is created. The record is kept on all the DNS servers that direct the web traffic worldwide, thus they all will identify if an email message comes from an authentic server or not. The verification is done at the very first server where the email goes through and in the first case the message is forwarded, but in the second it's discarded and it never gets to its intended recipient. Using SPF records for your domain names will stop all unauthorized people from using your email addresses for harmful objectives.