SPF, which is short for Sender Policy Framework, is an email security system, which is employed to confirm if an email message was sent by a certified server. Using SPF protection for a given domain name will prevent the faking of email addresses made with the domain. In simple words: enabling this function for a domain name generates a special record in the Domain Name System (DNS) containing the IP addresses of the servers which are allowed to send e-mails from mailboxes under the domain. The moment this record propagates worldwide, it will exist on all of the DNS servers that direct the Internet traffic. Whenever some email message is sent, the initial DNS server it goes through checks whether it originates from an approved server. If it does, it's forwarded to the destination address, however 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 email address then make it appear as if you're distributing spam messages. This approach is also known as email spoofing.