Sender Policy Framework, or SPF, is a verification system, which is used to prevent the so-called email spoofing where an e-mail message is sent from one address, but to appear as being sent from another, often with the idea to fraud the recipient in some way. When SPF protection is activated for a domain name, a unique record is made for it in the Domain Name System and all the DNS servers around the world get it. The record includes all of the mail servers that are permitted to send authentic messages from an address under the domain. When a message is sent, the first DNS server it encounters verifies the SPF record and when the sending server is authorized, the message is forwarded to the target destination. When, however, the sending server doesn't exist in the SPF record for the specified domain, the message won't be forwarded and it will be discarded. When you use this service, it will stop third parties from sending spam messages which appear to have been sent by you.