SPF, which means Sender Policy Framework, is an email security system, that is designed to verify whether an e-mail message was sent by a certified server. Using SPF protection for a domain will stop the faking of email addresses made with the domain. In simple words: enabling this attribute for a domain name creates a special record in the Domain Name System (DNS) that contains the IP of the servers that are permitted to send e-mails from mailboxes under the domain. The moment this record propagates worldwide, it exists on all DNS servers that route the Internet traffic. When some email message is sent, the initial DNS server it uses verifies whether it originates from an official server. When it does, it's forwarded to the destination address, yet if it doesn't originate from a server indexed in the SPF record for the domain, it is discarded. In this way nobody can mask an email address and make it look as if you're e-mailing spam messages. This technique is also known as email spoofing.