Sender Policy Framework, or SPF, is a validation system, that is designed to prevent the so-called e-mail spoofing where an e-mail message can be sent from one address, but to seem as being sent from a different, typically with the purpose to fraud the recipient for some reason. When SPF protection is activated for a domain name, a unique record is made for it in the Domain Name System and all of the DNS servers worldwide have it. The record contains all e-mail servers that are allowed to send valid messages from an e-mail address part of the domain. When a message is sent, the very first DNS server it goes to checks the SPF record and when its sending server is permitted, the message is sent to the targeted destination. If, however, the sending server is not included in the SPF record for the specified domain, the e-mail message won't be forwarded and it will be removed. In case you employ this solution, it will stop third parties from sending spam emails that look as if they have been sent from you.