SPF, which is short for Sender Policy Framework, is an email security system, which is used to validate whether an e-mail message is sent by an authorized server. Employing SPF protection for a given domain will prevent the forging of email addresses made with the domain. In simple words: enabling this feature for a domain makes a special record in the Domain Name System (DNS) that contains the IP addresses of the servers which are allowed to send email messages from mail boxes under the domain. As soon as this record propagates globally, it will exist on all DNS servers that route the Internet traffic. Whenever a new e-mail message is sent, the first DNS server it uses verifies whether it comes from an approved server. When it does, it is sent to the destination address, yet when it does not originate from a server indexed in the SPF record for the domain, it's rejected. In this way nobody will mask an e-mail address and make it look as if you are e-mailing spam messages. This approach is also identified as email spoofing.