Sender Policy Framework, or SPF, is a verification system, which is designed to stop the so-called e-mail spoofing where an e-mail message is sent from one email address, but to seem as being sent from a different, often with the objective to scam the recipient for some reason. When SPF protection is activated for a domain name, a specific record is created for it in the Domain Name System and all of the DNS servers worldwide have it. The record features all the mail servers that are allowed to send authentic messages from an email address under the domain. When an e-mail is sent, the very first DNS server it goes to checks the SPF record and in case its sending server is authorized, the message is forwarded to the targeted destination. In case, however, the sending server is not contained in the SPF record for the specified domain, the email message won't be sent and it will be removed. If you use this solution, it'll stop third parties from sending spam emails that seem to have been sent by you.