SPF, which stands for Sender Policy Framework, is an e-mail safety system, that is used to verify if an e-mail message was sent by an official server. Employing SPF protection for a domain will prevent the forging of email addresses generated with the domain. In simple words: enabling this attribute for a domain makes a special record in the Domain Name System (DNS) that contains the IP of the servers that are allowed to send emails from mailboxes under the domain. Once this record propagates worldwide, it exists on all DNS servers that route the Internet traffic. When an e-mail message is sent, the first DNS server it goes through checks if it comes from an authorized server. If it does, it's forwarded to the destination address, yet when it does not come 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 email address then make it look as if you are distributing spam. This technique is also termed email spoofing.