SPF, which means Sender Policy Framework, is an email security system, that is employed to verify if an e-mail message is sent by a certified server. Using SPF protection for a given domain name will stop the counterfeiting of email addresses generated with the domain. In layman's terms: activating this attribute for a domain name makes a particular record in the Domain Name System (DNS) which includes the IP of the servers that are allowed to send emails from mail boxes using the domain. When this record propagates worldwide, it exists on all DNS servers that route the Internet traffic. Any time some email message is sent, the initial DNS server it uses tests whether it comes from an official server. If it does, it is sent to the destination address, but when it does not come from a server listed in the SPF record for the particular domain, it is rejected. Thus nobody will mask an e-mail address and make it look as if you're sending spam. This technique is also termed email spoofing.