SPF, which means Sender Policy Framework, is an e-mail security system, that is designed to verify whether an e-mail message is sent by an authorized server. Employing SPF protection for a given domain name will stop the forging of email addresses made with the domain. In layman's terms: activating this feature for a domain makes a special record in the Domain Name System (DNS) containing the IP addresses of the servers which are allowed to send emails from mailboxes using the domain. The moment this record propagates worldwide, it will exist on all the DNS servers that route the Internet traffic. Every time an email message is sent, the first DNS server it uses verifies whether it originates from an accredited server. If it does, it is forwarded to the destination address, however if it doesn't originate from a server part of the SPF record for the particular domain, it is discarded. Thus nobody will be able to mask an email address to make it appear as if you are sending spam. This method is also termed email spoofing.