SPF, which stands for Sender Policy Framework, is an e-mail protection system, which is employed to confirm whether an e-mail message was sent by a certified server. Using SPF protection for a domain will stop the faking of email addresses generated with the domain. In simple words: activating this attribute for a domain creates a specific record in the Domain Name System (DNS) containing the IP of the servers that are allowed to send emails from mail boxes using the domain. As soon as this record propagates worldwide, it will exist on all the DNS servers that direct the Internet traffic. Any time an e-mail message is sent, the initial DNS server it goes through checks if it comes from an official server. In the event it does, it is sent to the destination address, but if it does not come from a server indexed in the SPF record for the particular domain, it's rejected. Thus nobody will be able to mask an email address to make it look as if you are distributing spam. This technique is also called email spoofing.