Sender Policy Framework, or SPF, is a verification system, that is employed to stop the so-called e-mail spoofing where an email message can be sent from one email, but to seem as being sent from a different one, usually with the objective to fraud the recipient in some way. If SPF protection is enabled for a domain name, a unique record is made for it in the Domain Name System and all the DNS servers around the world receive it. The record contains all e-mail servers that are permitted to send valid messages from an address part of the domain. When an e-mail is sent, the first DNS server it goes to checks the SPF record and in case its sending server is permitted, the message is sent to the target receiver. In case, however, the sending server is not included in the SPF record for the given domain, the email message won't be forwarded and it will be discarded. In the event that you use this solution, it will prevent third parties from sending spam messages that seem to have been sent by you.