SPF, which abbreviates Sender Policy Framework, is a verification system that aims at stopping the so-called e-mail counterfeiting. Basically, this indicates sending a message from one email address and making it appear to be sent from another one with the objective to scam in some manner the individual receiving it. In case the SPF protection is activated for a domain, a record which contains all the mail servers authorized to send messages with addresses in the domain is created. The record is kept on all of the DNS servers that route the web traffic globally, so they all will recognize whether an email message comes from an authentic server or not. The check is done at the very first server where the email goes through and in the first case the e-mail message is forwarded, whereas in the second it is discarded and it never gets to its intended recipient. Using SPF records for your domains will stop any unauthorized people from making use of your email addresses for harmful purposes.