Sender Policy Framework, or SPF, is a validation system, that is used to prevent the so-called email spoofing where an e-mail message can be sent from one e-mail address, but to look as being sent from another, ordinarily with the objective to scam the recipient in some way. When SPF protection is activated for a domain, a special record is created for it in the Domain Name System and all of the DNS servers around the world get it. The record includes all of the e-mail servers that are allowed to send legitimate messages from an email address part of the domain. When an email is sent, the first DNS server it goes to verifies the SPF record and if its sending server is authorized, the message is sent to the target receiver. When, however, the sending server is not included in the SPF record for the particular domain, the e-mail message will not be forwarded and it will be discarded. In the event that you employ this service, it will prevent third parties from sending spam that seem to have been sent by you.