Sender Policy Framework, or SPF, is a verification system, that is employed to stop the so-called email spoofing where an email message can be sent from one e-mail address, but to appear as being sent from a different one, usually with the purpose to fraud the recipient in some way. If SPF protection is activated for a domain name, an exclusive record is generated for it in the Domain Name System and all the DNS servers worldwide have it. The record includes all mail servers that are permitted to send legitimate messages from an address under the domain. When a message is sent, the first DNS server it encounters verifies the SPF record and in case the sending server is permitted, the message is forwarded to the targeted destination. In case, however, the sending server is not present in the SPF record for the given domain, the email message will not be forwarded and it will be discarded. When you use this solution, it'll stop third parties from sending spam emails that look as if they have been sent by you.