SPF, which stands for Sender Policy Framework, is an email security system, that is used to verify if an e-mail message is sent by a licensed server. Employing SPF protection for a particular domain will stop the faking of email addresses created with the domain. In simple words: enabling this feature for a domain name creates a specific record in the Domain Name System (DNS) containing the IP of the servers which are permitted to send e-mail messages from mail boxes using the domain. When this record propagates globally, it exists on all the DNS servers that route the Internet traffic. When some email message is sent, the first DNS server it uses verifies whether it originates from an official server. When it does, it's sent to the destination address, but when it doesn't originate from a server indexed in the SPF record for the domain, it is rejected. Thus nobody will be able to mask an email address to make it look as if you're distributing spam. This technique is also referred to as email spoofing.