SPF, which means Sender Policy Framework, is an email security system, which is is intended to validate if an e-mail message is sent by an official server. Using SPF protection for a domain name will prevent the forging of email addresses generated with the domain. In layman's terms: activating this function for a domain name makes a particular record in the Domain Name System (DNS) containing the IP of the servers that are permitted to send e-mail messages from mail boxes using the domain. As soon as this record propagates globally, it will exist on all the DNS servers that route the Internet traffic. Whenever an email message is sent, the initial DNS server it uses verifies whether it comes from an authorized server. In the event it does, it's sent to the destination address, but if it doesn't originate from a server indexed in the SPF record for the particular domain, it is discarded. Thus nobody will mask an email address to make it look as if you are distributing spam messages. This method is also termed email spoofing.