SPF, which stands for Sender Policy Framework, is an email security system, that is employed to validate whether an email message is sent by a certified server. Using SPF protection for a particular domain will stop the counterfeiting of emails created with the domain. In layman's terms: enabling this function for a domain generates a specific record in the Domain Name System (DNS) that contains the IP of the servers that are allowed to send e-mail messages from mailboxes using the domain. The moment this record propagates worldwide, it will exist on all DNS servers that route the Internet traffic. When some email message is sent, the first DNS server it goes through tests if it originates from an approved server. If it does, it's forwarded to the destination address, yet if it does not come from a server part of the SPF record for the domain, it is discarded. Thus nobody will mask an email address and make it appear as if you are e-mailing spam messages. This method is also known as email spoofing.