SPF, which is an acronym for Sender Policy Framework, is an email security system, which is designed to verify whether an e-mail message was sent by a certified server. Employing SPF protection for a given domain name will stop the forging of emails generated with the domain. In simple words: activating this feature for a domain name generates a specific record in the Domain Name System (DNS) which includes the IP addresses of the servers which are permitted to send e-mails from mailboxes under the domain. When this record propagates worldwide, it will exist on all of the DNS servers that route the Internet traffic. Any time an email message is sent, the initial DNS server it goes through checks if it originates from an official server. In the event it does, it's sent to the destination address, however when it doesn't originate from a server indexed in the SPF record for the domain, it is discarded. In this way nobody can mask an e-mail address and make it appear as if you are distributing spam. This technique is also termed email spoofing.