SPF, which is short for Sender Policy Framework, is an email protection system, that is designed to validate whether an e-mail message was sent by a licensed server. Employing SPF protection for a domain will prevent the faking of email addresses generated with the domain. In layman's terms: activating this function for a domain name generates a specific record in the Domain Name System (DNS) that contains the IP of the servers which are allowed to send e-mails from mail boxes under the domain. As soon as this record propagates globally, it will exist on all the DNS servers that route the Internet traffic. Any time an e-mail message is sent, the first DNS server it goes through tests if it originates from an approved server. If it does, it's forwarded to the destination address, however if it doesn't come from a server listed in the SPF record for the particular domain, it is discarded. Thus nobody will be able to mask an email address and make it appear as if you're sending spam messages. This technique is also identified as email spoofing.