Sender Policy Framework, or SPF, is a validation system, that is employed to prevent the so-called email spoofing where an e-mail message can be sent from one e-mail, but to look as being sent from a different one, typically with the idea to scam the recipient for some reason. If SPF protection is activated for a domain name, a unique record is generated for it in the Domain Name System and all DNS servers worldwide have it. The record includes all of the e-mail servers that are permitted to send authentic messages from an address within the domain. When a message is sent, the first DNS server it goes to checks the SPF record and in case the sending server is permitted, the message is forwarded to the targeted destination. When, however, the sending server is not contained in the SPF record for the given domain, the email message won't be forwarded and it'll be discarded. In case you employ this solution, it'll stop third parties from sending spam which appear to have been sent by you.