Sender Policy Framework, or SPF, is a validation system, that is intended to prevent the so-called e-mail spoofing where an e-mail message is sent from one e-mail address, but to look as being sent from a different one, frequently with the purpose to scam the recipient for some reason. If SPF protection is activated for a domain name, a specific record is created for it in the Domain Name System and all the DNS servers worldwide have it. The record contains all of the e-mail servers that are permitted to send legitimate messages from an email address under the domain. When a message is sent, the very first DNS server it encounters checks the SPF record and in case its 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 particular domain, the message will not be forwarded and it'll be removed. When you use this solution, it will stop third parties from sending spam emails that seem to have been sent from you.