SPF, which means Sender Policy Framework, is an e-mail security system, that is used to confirm if an e-mail message was sent by a licensed server. Using SPF protection for a given domain name will stop the forging of email addresses made with the domain. In layman's terms: activating this feature for a domain generates a specific record in the Domain Name System (DNS) containing the IP of the servers which are allowed to send emails from mailboxes under the domain. The moment this record propagates globally, it exists on all of the DNS servers that route the Internet traffic. Any time an email message is sent, the initial DNS server it uses tests if it comes from an authorized server. In the event it does, it's forwarded to the destination address, but if it doesn't come from a server indexed in the SPF record for the particular domain, it's discarded. In this way nobody will mask an e-mail address to make it appear as if you are distributing spam. This technique is also identified as email spoofing.