Sender Policy Framework, or SPF, is a validation system, that is employed to stop the so-called email spoofing where an email message is sent from one address, but to seem as being sent from a different one, usually with the objective 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 the DNS servers worldwide have it. The record features all the mail servers that are allowed to send valid messages from an e-mail address part of the domain. When a message is sent, the first DNS server it goes to verifies the SPF record and when the sending server is permitted, the message is forwarded to the targeted receiver. In case, however, the sending server is not present in the SPF record for the particular domain, the message won't be sent and it will be discarded. When you employ this solution, it'll prevent third parties from sending spam e-mails which seem to have been sent by you.