SPF, which means Sender Policy Framework, is an e-mail protection system, that is used to verify whether an e-mail message was sent by a licensed server. Employing SPF protection for a given domain name will prevent the counterfeiting of email addresses made with the domain. In simple words: enabling this attribute for a domain makes a specific record in the Domain Name System (DNS) which contains the IP addresses of the servers which are allowed to send e-mail messages from mailboxes using the domain. Once this record propagates globally, it exists on all of the DNS servers that direct the Internet traffic. When an e-mail message is sent, the first DNS server it uses checks if it originates from an accredited server. In the event it does, it is sent to the destination address, yet when it does not originate from a server listed in the SPF record for the domain, it's discarded. Thus nobody can mask an e-mail address to make it appear as if you are distributing spam. This method is also referred to as email spoofing.
