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 can be sent from one e-mail, but to seem as being sent from a different, ordinarily with the objective to fraud the recipient for some reason. If SPF protection is activated for a domain, a specific record is generated for it in the Domain Name System and all the DNS servers around the world get it. The record features all email servers that are allowed to send legitimate messages from an email address part of 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 permitted, the message is sent to the target destination. In case, however, the sending server is not present in the SPF record for the particular domain, the e-mail message won't be forwarded and it will be discarded. In case you employ this service, it will stop third parties from sending spam messages that appear to have been sent from you.