Sender Policy Framework, or SPF, is a validation system, which is intended to prevent the so-called e-mail spoofing where an e-mail message is sent from one e-mail address, but to seem as being sent from another one, frequently with the objective to fraud the recipient in some way. If SPF protection is activated for a domain name, a specific record is created for it in the Domain Name System and all DNS servers worldwide get it. The record includes all of the e-mail servers that are allowed to send valid messages from an e-mail 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 the sending server is authorized, the message is sent to the target destination. When, however, the sending server is not included in the SPF record for the given domain, the e-mail message will not be sent and it will be discarded. If you employ this service, it will prevent third parties from sending spam emails which appear to have been sent from you.