SPF, which means Sender Policy Framework, is an e-mail security system, that is used to confirm if an email message was sent by an authorized server. Employing SPF protection for a domain will stop the forging of emails generated with the domain. In simple words: enabling this function for a domain generates a particular record in the Domain Name System (DNS) which contains the IP of the servers that are permitted to send e-mail messages from mailboxes under the domain. As soon as this record propagates worldwide, it will exist on all the DNS servers that route the Internet traffic. Every time an email message is sent, the initial DNS server it goes through verifies whether it comes from an official server. If it does, it is forwarded to the destination address, but when it doesn't originate from a server indexed in the SPF record for the domain, it is rejected. In this way nobody can mask an e-mail address to make it look as if you are sending spam. This technique is also known as email spoofing.