SPF, which is an acronym for Sender Policy Framework, is an e-mail protection system, that is designed to verify whether an e-mail message is sent by a licensed server. Employing SPF protection for a particular domain will prevent the counterfeiting of email addresses made with the domain. In simple words: enabling this feature for a domain generates a specific record in the Domain Name System (DNS) that contains the IP of the servers which are permitted to send e-mail messages from mail boxes under the domain. As soon as this record propagates globally, it exists on all the DNS servers that direct the Internet traffic. Whenever a new e-mail message is sent, the first DNS server it uses checks whether it originates from an approved server. In the event it does, it is sent to the destination address, but when it doesn't come from a server indexed in the SPF record for the domain, it's rejected. Thus nobody can mask an email address to make it appear as if you are e-mailing spam messages. This approach is also termed email spoofing.
