Sender Policy Framework, or SPF, is a verification system, which is employed to stop the so-called e-mail spoofing where an e-mail message is sent from one e-mail, but to appear as being sent from a different one, usually with the idea to scam the recipient someway. If SPF protection is activated for a domain, an exclusive record is created for it in the Domain Name System and all the DNS servers around the world have it. The record includes all the e-mail servers that are allowed to send legitimate messages from an e-mail address within the domain. When an e-mail is sent, the very first DNS server it goes to checks the SPF record and if its sending server is permitted, the message is forwarded to the targeted receiver. If, however, the sending server is not present in the SPF record for the specified domain, the e-mail message won't be submitted and it will be discarded. In the event that you employ this service, it will stop third parties from sending spam e-mails that look as if they have been sent by you.