SPF, which means Sender Policy Framework, is an e-mail security system, that is is intended to confirm whether an e-mail message is sent by an authorized server. Using SPF protection for a domain name will prevent the forging of emails made with the domain. In simple words: enabling this function for a domain makes a particular record in the Domain Name System (DNS) which includes the IP of the servers that are allowed to send e-mail messages from mail boxes using the domain. When this record propagates globally, it will exist on all the DNS servers that direct the Internet traffic. When an e-mail message is sent, the first DNS server it goes through checks whether it comes from an official server. When it does, it's forwarded to the destination address, yet when it does not come from a server part of the SPF record for the domain, it is rejected. In this way nobody will be able to mask an e-mail address and make it look as if you are sending spam. This approach is also known as email spoofing.