SPF, which is short for Sender Policy Framework, is an e-mail protection system, that is designed to verify whether an email message was sent by a licensed server. Using SPF protection for a particular domain will stop the forging of emails made with the domain. In layman's terms: enabling this attribute for a domain name generates a particular record in the Domain Name System (DNS) that contains the IP of the servers that are allowed to send emails from mail boxes using the domain. As soon as this record propagates worldwide, it exists on all DNS servers that direct the Internet traffic. Every time an e-mail message is sent, the initial DNS server it goes through tests whether it comes from an accredited server. When it does, it's sent to the destination address, but when it doesn't come from a server indexed in the SPF record for the domain, it's discarded. In this way nobody will mask an e-mail address to make it look as if you're distributing spam. This method is also known as email spoofing.