SPF, which means Sender Policy Framework, is an email protection system, which is is intended to verify if an email message was sent by a certified server. Using SPF protection for a given domain will prevent the forging of email addresses created with the domain. In simple words: enabling this function for a domain name generates a particular record in the Domain Name System (DNS) which includes the IP addresses of the servers that are permitted to send email messages from mailboxes under the domain. Once this record propagates globally, it will exist on all the DNS servers that route the Internet traffic. When some email message is sent, the initial DNS server it uses tests whether it comes from an authorized server. In the event it does, it's sent to the destination address, but if it does not come from a server part of the SPF record for the domain, it's rejected. Thus nobody will be able to mask an e-mail address to make it appear as if you're e-mailing spam. This approach is also known as email spoofing.