Sender Policy Framework, or SPF, is a validation system, that is intended to prevent the so-called email spoofing where an email message is sent from one e-mail, but to seem as being sent from another one, generally with the idea to fraud the recipient in some way. When SPF protection is enabled for a domain name, a unique record is made for it in the Domain Name System and all of the DNS servers globally get it. The record contains all of the email servers that are permitted to send valid messages from an e-mail address part of the domain. When an email is sent, the first DNS server it goes to checks the SPF record and in case its sending server is authorized, the message is sent to the targeted destination. If, however, the sending server doesn't exist in the SPF record for the given domain, the message will not be forwarded and it will be removed. Whenever you employ this solution, it will prevent third parties from sending spam which seem to have been sent by you.