SPF, which is an acronym for Sender Policy Framework, is an e-mail protection system, that is used to verify whether an email message was sent by a certified server. Using SPF protection for a particular domain name will prevent the faking of emails created with the domain. In layman's terms: activating this feature for a domain creates a particular record in the Domain Name System (DNS) which contains the IP of the servers that are allowed to send emails from mail boxes under the domain. As soon as this record propagates worldwide, it will exist on all the DNS servers that route the Internet traffic. When some e-mail message is sent, the first DNS server it goes through checks whether it comes from an official server. When it does, it's sent to the destination address, yet when it does not come from a server part of the SPF record for the domain, it is discarded. Thus nobody will be able to mask an e-mail address then make it look as if you are distributing spam. This approach is also known as email spoofing.