SPF, which abbreviates Sender Policy Framework, is a certification system that aims at preventing the so-called e-mail counterfeiting. In simple terms, this means sending some message from one e-mail and making it look like it’s sent from a different one with the idea to scam in some way the individual getting it. In case the SPF protection is activated for a domain, a record which contains all of the mail servers authorized to email messages with addresses in the domain is created. The record is stored on all of the DNS servers that route the Internet traffic worldwide, therefore they all can recognize if an email message originates from a valid server or not. The check is conducted at the first server where the email goes through and in the first case the message is forwarded, whereas in the second one it is discarded and it never reaches the intended recipient. Applying SPF records for your domains will stop all unwanted people from making use of your emails for malicious purposes.