Sender Policy Framework, or SPF, is a verification system, which is intended to stop the so-called e-mail spoofing where an e-mail message is sent from one e-mail address, but to appear as being sent from another, ordinarily with the idea to scam the recipient in some way. If SPF protection is enabled for a domain name, a specific record is made for it in the Domain Name System and all of the DNS servers worldwide receive it. The record contains all the e-mail servers that are allowed to send legitimate messages from an email address under the domain. When an e-mail is sent, the first DNS server it goes to verifies the SPF record and in case its sending server is authorized, the message is forwarded to the target receiver. When, however, the sending server is not present in the SPF record for the specified domain, the email message will not be sent and it'll be discarded. If you employ this solution, it'll stop third parties from sending spam messages which appear to have been sent by you.