Sender Policy Framework, or SPF, is a validation system, that is used to stop the so-called email spoofing where an e-mail message can be sent from one address, but to look as being sent from another, frequently with the purpose to fraud the recipient someway. If SPF protection is enabled for a domain, a specific record is made for it in the Domain Name System and all the DNS servers worldwide get it. The record contains all the e-mail servers that are permitted to send valid messages from an address part of the domain. When an e-mail is sent, the very first DNS server it goes to checks the SPF record and if the sending server is permitted, the message is sent to the target receiver. If, however, the sending server is not included in the SPF record for the specified domain, the message won't be submitted and it'll be removed. When you employ this solution, it'll stop third parties from sending spam emails which appear to have been sent by you.