Sender Policy Framework, or SPF, is a verification system, which is designed to prevent the so-called email spoofing where an email message can be sent from one email, but to look as being sent from a different, usually with the objective to fraud the recipient for some reason. When SPF protection is enabled for a domain name, a specific record is made for it in the Domain Name System and all DNS servers around the world have it. The record includes all the email servers that are allowed to send legitimate messages from an e-mail address part of the domain. When a message is sent, the very first DNS server it goes to verifies the SPF record and if its sending server is permitted, the message is sent to the target destination. In case, however, the sending server is not contained in the SPF record for the particular domain, the message will not be forwarded and it will be removed. When you use this service, it'll stop third parties from sending spam emails that seem to have been sent from you.