Sender Policy Framework, or SPF, is a validation system, which is employed to stop the so-called email spoofing where an e-mail message can be sent from one e-mail, but to seem as being sent from a different one, generally with the objective to fraud the recipient someway. When SPF protection is activated for a domain, a specific record is made for it in the Domain Name System and all the DNS servers globally get it. The record includes all the email servers that are permitted to send legitimate messages from an e-mail address under the domain. When an email is sent, the very first DNS server it goes to checks the SPF record and when its sending server is authorized, the message is forwarded to the target destination. In case, however, the sending server is not included in the SPF record for the given domain, the email message will not be submitted and it'll be removed. In the event that you use this service, it will stop third parties from sending spam messages which look as if they have been sent by you.