SPF, which is short for Sender Policy Framework, is an email security system, which is is intended to verify whether an e-mail message was sent by an official server. Using SPF protection for a particular domain will stop the faking of email addresses generated with the domain. In layman's terms: activating this attribute for a domain name generates a special record in the Domain Name System (DNS) which includes the IP of the servers that are allowed to send email messages from mailboxes under the domain. Once this record propagates worldwide, it exists on all DNS servers that direct the Internet traffic. Every time an e-mail message is sent, the initial DNS server it goes through checks whether it originates from an approved server. If it does, it is forwarded to the destination address, however when it doesn't originate from a server indexed in the SPF record for the domain, it's discarded. In this way nobody will mask an email address then make it look as if you are sending spam messages. This technique is also known as email spoofing.