Sender Policy Framework, or SPF, is a verification system, which is used to stop the so-called e-mail spoofing where an e-mail message can be sent from one e-mail address, but to seem as being sent from a different, frequently with the purpose to fraud the recipient in some way. If SPF protection is enabled for a domain name, a unique record is generated for it in the Domain Name System and all the DNS servers around the world have it. The record includes all the mail servers that are permitted to send valid messages from an email address under the domain. When an e-mail is sent, the first DNS server it encounters verifies the SPF record and if the sending server is authorized, the message is sent to the target receiver. When, however, the sending server is not present in the SPF record for the specified domain, the e-mail message will not be forwarded and it'll be discarded. Whenever you employ this service, it will stop third parties from sending spam e-mails which look as if they have been sent by you.