SPF, which is short for Sender Policy Framework, is an email safety system, that is used to confirm if an email message is sent by a licensed server. Employing SPF protection for a domain will stop the forging of email addresses made with the domain. In simple words: activating this function for a domain name makes a special record in the Domain Name System (DNS) containing the IP addresses of the servers that are allowed to send e-mail messages from mailboxes using the domain. The moment this record propagates worldwide, it exists on all the DNS servers that route the Internet traffic. When some email message is sent, the initial DNS server it goes through tests whether it comes from an official server. If it does, it is sent to the destination address, but when it does not originate from a server indexed in the SPF record for the domain, it's rejected. In this way nobody can mask an email address and make it look as if you are sending spam messages. This technique is also known as email spoofing.