SPF, which is short for Sender Policy Framework, is an e-mail security system, that is employed to validate if an e-mail message is sent by an official server. Using SPF protection for a given domain will prevent the forging of emails made with the domain. In layman's terms: activating this attribute for a domain creates a special record in the Domain Name System (DNS) which contains the IP addresses of the servers which are permitted to send email messages from mail boxes under the domain. The moment this record propagates globally, it exists on all the DNS servers that route the Internet traffic. Whenever some e-mail message is sent, the initial DNS server it goes through verifies if it originates from an authorized server. If it does, it is sent to the destination address, however if it does not originate from a server listed in the SPF record for the particular domain, it is discarded. In this way nobody will mask an email address and make it look as if you're e-mailing spam. This technique is also called email spoofing.