SPF, which is short for Sender Policy Framework, is an email security system, which is designed to verify if an e-mail message was sent by a licensed server. Employing SPF protection for a given domain will stop the counterfeiting of email addresses made with the domain. In layman's terms: activating this feature for a domain name makes a special record in the Domain Name System (DNS) which includes the IP addresses of the servers that are permitted to send email messages from mailboxes under the domain. When this record propagates globally, it exists on all DNS servers that direct the Internet traffic. Any time some e-mail message is sent, the first DNS server it goes through checks whether it originates from an accredited server. If it does, it is forwarded to the destination address, but when it does not originate from a server indexed in the SPF record for the particular domain, it's rejected. Thus nobody will mask an email address to make it appear as if you're distributing spam. This approach is also called email spoofing.