SPF, which stands for Sender Policy Framework, is an e-mail security system, which is employed to confirm if an email message is sent by a licensed server. Using SPF protection for a given domain will stop the forging of emails generated with the domain. In simple words: enabling this feature for a domain generates a particular record in the Domain Name System (DNS) which contains the IP of the servers which are permitted to send e-mails from mailboxes under the domain. The moment this record propagates globally, it will exist on all of the DNS servers that route the Internet traffic. Every time a new email message is sent, the first DNS server it goes through verifies whether it comes from an accredited server. In the event it does, it's sent to the destination address, but if it doesn't come from a server indexed in the SPF record for the domain, it's rejected. Thus nobody can mask an email address and make it appear as if you are distributing spam. This technique is also referred to as email spoofing.