SPF, which stands for Sender Policy Framework, is an email safety system, which is designed to validate if an e-mail message is sent by a licensed server. Using SPF protection for a given domain name will prevent the counterfeiting of email addresses made with the domain. In simple words: enabling this function for a domain name makes a particular record in the Domain Name System (DNS) which contains the IP addresses of the servers which are permitted to send e-mails from mail boxes using the domain. The moment this record propagates worldwide, it will exist on all DNS servers that direct the Internet traffic. When a new email message is sent, the initial DNS server it goes through tests whether it comes from an accredited server. When it does, it is forwarded to the destination address, however when it does not come from a server part of the SPF record for the domain, it's rejected. Thus nobody will be able to mask an email address and make it appear as if you're sending spam messages. This approach is also called email spoofing.