SPF, which stands for Sender Policy Framework, is an email safety system, which is designed to validate if an email message was sent by a licensed server. Employing SPF protection for a particular domain will stop the forging of email addresses generated with the domain. In layman's terms: enabling this feature for a domain makes a specific record in the Domain Name System (DNS) which includes the IP addresses of the servers which are allowed to send e-mail messages from mailboxes under the domain. When this record propagates worldwide, it exists on all the DNS servers that direct the Internet traffic. Every time a new e-mail message is sent, the initial DNS server it goes through tests whether it comes from an approved server. When it does, it's sent to the destination address, but if it doesn't come from a server part of the SPF record for the domain, it's rejected. In this way nobody will mask an e-mail address and make it appear as if you're distributing spam messages. This technique is also referred to as email spoofing.