SPF, which is an acronym for Sender Policy Framework, is an email security system, which is is intended to verify if an e-mail message was sent by an authorized server. Employing SPF protection for a given domain will prevent the forging of emails created with the domain. In layman's terms: activating this feature for a domain makes a special record in the Domain Name System (DNS) which contains the IP addresses of the servers which are allowed to send emails from mailboxes using the domain. As soon as this record propagates globally, it will exist on all DNS servers that route the Internet traffic. Any time a new e-mail message is sent, the first DNS server it goes through verifies if it comes from an official server. If it does, it's sent to the destination address, but if it doesn't come from a server listed in the SPF record for the domain, it's rejected. In this way nobody will mask an e-mail address then make it look as if you're e-mailing spam messages. This method is also referred to as email spoofing.