SPF, which stands for Sender Policy Framework, is an email security system, that is employed to confirm whether an e-mail message was sent by a licensed server. Employing SPF protection for a domain will prevent the forging of emails created with the domain. In simple words: activating this attribute for a domain generates a special record in the Domain Name System (DNS) containing the IP of the servers that are permitted to send emails from mailboxes under the domain. When this record propagates globally, it will exist on all DNS servers that route the Internet traffic. Every time some email message is sent, the initial DNS server it goes through verifies whether it comes from an official server. When it does, it's sent to the destination address, but if it does not originate from a server listed in the SPF record for the domain, it's discarded. Thus nobody will be able to mask an e-mail address and make it appear as if you're sending spam. This approach is also known as email spoofing.