SPF, which means Sender Policy Framework, is an e-mail protection system, which is employed to verify if an email message was sent by an official server. Employing SPF protection for a domain will prevent the counterfeiting of email addresses created with the domain. In simple words: activating this function for a domain name creates a specific record in the Domain Name System (DNS) which includes the IP addresses of the servers which are allowed to send emails from mailboxes under the domain. When this record propagates worldwide, it exists on all the DNS servers that direct the Internet traffic. Every time a new e-mail message is sent, the first DNS server it goes through verifies if it comes from an accredited server. If it does, it's sent to the destination address, however if it does not originate from a server part of the SPF record for the particular domain, it's rejected. In this way nobody can mask an e-mail address then make it appear as if you are distributing spam. This technique is also known as email spoofing.