SPF, which means Sender Policy Framework, is an e-mail security system, that is employed to confirm if an email message is sent by an official server. Using SPF protection for a particular domain will prevent the counterfeiting of email addresses made with the domain. In layman's terms: enabling this attribute for a domain makes a particular record in the Domain Name System (DNS) containing the IP addresses of the servers which are allowed to send e-mails from mail boxes using the domain. As soon as this record propagates globally, it exists on all of the DNS servers that route the Internet traffic. When some email message is sent, the initial DNS server it uses tests if it originates from an approved server. In the event it does, it's forwarded to the destination address, but if it does not originate from a server indexed in the SPF record for the particular domain, it is rejected. Thus nobody can mask an email address and make it appear as if you are sending spam messages. This technique is also referred to as email spoofing.