Sender Policy Framework, or SPF, is a validation system, that is designed to prevent the so-called e-mail spoofing where an e-mail message can be sent from one e-mail, but to appear as being sent from another, frequently with the idea to fraud the recipient for some reason. When SPF protection is enabled for a domain name, a unique record is made for it in the Domain Name System and all of the DNS servers globally have it. The record contains all the mail servers that are permitted to send authentic messages from an address within 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. In case, however, the sending server is not included in the SPF record for the particular domain, the e-mail message will not be sent and it'll be removed. When you use this service, it will prevent third parties from sending spam that seem to have been sent by you.