SPF, which abbreviates Sender Policy Framework, is a certification system that aims at blocking the so-called e-mail faking. In simple terms, this means sending a message from one e-mail and making it appear to be sent from another one with the purpose to scam in some way the person opening it. If the SPF protection is running for a domain, a record which includes all of the mail servers authorized to send messages with addresses in the domain is generated. The record is saved on all of the DNS servers that direct the web traffic worldwide, thus they all will recognize if an email message originates from a trustworthy 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, and in the second one it's discarded and it never reaches the intended recipient. Applying SPF records for your domain names will prevent all unwanted people from using your emails for malicious objectives.