Sender Policy Framework, or SPF, is a validation system, that is employed to prevent the so-called e-mail spoofing where an email message can be sent from one email, but to look as being sent from a different, frequently with the objective to fraud the recipient in some way. If SPF protection is enabled for a domain, a specific record is created for it in the Domain Name System and all the DNS servers globally receive it. The record includes all of the mail servers that are allowed to send valid messages from an email address part of the domain. When an email is sent, the first DNS server it goes to verifies the SPF record and in case its sending server is authorized, the message is forwarded 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 sent and it will be discarded. When you use this service, it'll stop third parties from sending spam messages that seem to have been sent by you.