SPF, which is an abbreviation for Sender Policy Framework, is a verification system that is aimed at stopping the so-called e-mail counterfeiting. In simple terms, it indicates sending a message from one e-mail and making it look like it’s sent from another one with the purpose to scam in some way the person getting it. When the SPF protection is active for a domain, a record that includes all mail servers authorized to send messages with addresses under the domain is created. The record is stored on all the DNS servers that route the web traffic all over the world, thus they all will recognize whether an email message originates from an authentic server or not. The verification is conducted at the first server where the email goes through and in the first case the e-mail message is forwarded, while in the second one it's removed and it never reaches the intended recipient. Employing SPF records for your domains will stop all unauthorized people from making use of your email addresses for harmful purposes.