SPF, which stands for Sender Policy Framework, is an email security system, that is designed to validate if an email message is sent by a licensed server. Using SPF protection for a domain will prevent the faking of email addresses generated with the domain. In simple words: enabling this function for a domain name generates a particular record in the Domain Name System (DNS) that 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 exists on all the DNS servers that direct the Internet traffic. Every time an e-mail message is sent, the initial DNS server it goes through tests whether it originates from an approved server. In the event it does, it is forwarded to the destination address, but if it does not come from a server part of the SPF record for the domain, it is rejected. In this way nobody will mask an e-mail address to make it appear as if you are e-mailing spam messages. This technique is also known as email spoofing.