SPF, which is short for Sender Policy Framework, is an e-mail security system, which is employed to verify if an email message was sent by a licensed server. Employing SPF protection for a particular domain will stop the forging of emails made with the domain. In simple words: activating this feature for a domain generates a particular record in the Domain Name System (DNS) containing the IP addresses of the servers which are allowed to send email messages from mail boxes under the domain. The moment this record propagates worldwide, it will exist on all DNS servers that direct the Internet traffic. Whenever an e-mail message is sent, the initial DNS server it goes through checks whether it comes from an accredited server. In the event it does, it is forwarded to the destination address, however when it doesn't originate from a server part of the SPF record for the particular domain, it's discarded. In this way nobody will be able to mask an e-mail address and make it appear as if you're sending spam messages. This technique is also known as email spoofing.