Sender Policy Framework, or SPF, is a validation system, which is employed to stop the so-called e-mail spoofing where an email message is sent from one address, but to look as being sent from another one, typically with the objective to scam the recipient for some reason. When SPF protection is activated for a domain, a specific record is created for it in the Domain Name System and all the DNS servers globally have it. The record features all e-mail servers that are allowed to send valid messages from an address under the domain. When an email is sent, the very first DNS server it goes to checks the SPF record and if the sending server is authorized, the message is forwarded to the targeted destination. When, however, the sending server is not contained in the SPF record for the specified domain, the message won't be forwarded and it will be discarded. In case you employ this solution, it'll stop third parties from sending spam emails which appear to have been sent from you.