SPF, which means Sender Policy Framework, is an e-mail security system, that is employed to confirm whether an e-mail message is sent by an official server. Employing SPF protection for a particular domain name will prevent the faking of emails created with the domain. In simple words: enabling this attribute for a domain creates a specific record in the Domain Name System (DNS) which includes the IP of the servers that are allowed to send e-mail messages from mail boxes under the domain. The moment this record propagates globally, it exists on all the DNS servers that direct the Internet traffic. Any time a new email message is sent, the first DNS server it goes through tests whether it comes from an accredited server. When it does, it's forwarded to the destination address, but when it doesn't originate from a server indexed in the SPF record for the particular domain, it's rejected. Thus nobody will mask an e-mail address to make it look as if you are e-mailing spam messages. This technique is also termed email spoofing.