Sender Policy Framework, or SPF, is a validation system, which is employed to stop the so-called email spoofing where an email message is sent from one email, but to look as being sent from a different one, ordinarily with the idea to scam the recipient someway. When SPF protection is activated for a domain name, an exclusive record is generated for it in the Domain Name System and all of the DNS servers worldwide get it. The record contains all of the email servers that are permitted to send legitimate messages from an e-mail address within the domain. When an e-mail is sent, the first DNS server it encounters verifies the SPF record and when the sending server is authorized, the message is sent to the target destination. In case, however, the sending server is not included in the SPF record for the given domain, the message won't be forwarded and it'll be removed. In case you use this service, it'll stop third parties from sending spam messages which look as if they have been sent by you.