SPF, which is short for Sender Policy Framework, is an email safety system, which is is intended to validate whether an e-mail message is sent by a certified server. Using SPF protection for a given domain name will prevent the forging of emails generated with the domain. In simple words: enabling this feature for a domain makes a special record in the Domain Name System (DNS) which includes the IP addresses of the servers which are allowed to send e-mail messages from mailboxes using the domain. The moment this record propagates globally, it will exist on all of the DNS servers that route the Internet traffic. Every time a new email message is sent, the first DNS server it goes through tests whether it comes from an accredited server. In the event it does, it is sent to the destination address, yet if it doesn't come from a server indexed in the SPF record for the particular domain, it is rejected. In this way nobody will be able to mask an e-mail address then make it look as if you're sending spam. This technique is also termed email spoofing.