Sender Policy Framework, or SPF, is a verification system, that is employed to stop the so-called email spoofing where an email message is sent from one email, but to seem as being sent from another one, generally with the idea to fraud the recipient in some way. If SPF protection is enabled for a domain, a unique record is generated for it in the Domain Name System and all DNS servers worldwide receive it. The record contains all the e-mail servers that are permitted to send valid messages from an email address within the domain. When a message is sent, the very first DNS server it goes to checks the SPF record and when its sending server is permitted, the message is forwarded to the target destination. If, however, the sending server doesn't exist in the SPF record for the particular domain, the email message will not be forwarded and it'll be discarded. Whenever you use this solution, it'll prevent third parties from sending spam emails which seem to have been sent by you.