Sender Policy Framework, or SPF, is a verification system, that is used to prevent the so-called e-mail spoofing where an email message is sent from one e-mail address, but to appear as being sent from a different one, ordinarily with the purpose to fraud the recipient for some reason. If SPF protection is enabled for a domain, an exclusive record is made for it in the Domain Name System and all of the DNS servers around the world receive it. The record includes all the e-mail servers that are permitted to send legitimate messages from an e-mail address part of the domain. When an email is sent, the first DNS server it encounters verifies the SPF record and when its sending server is authorized, the message is forwarded to the targeted receiver. If, however, the sending server is not contained in the SPF record for the specified domain, the email message will not be forwarded and it will be removed. In case you use this service, it will stop third parties from sending spam emails which look as if they have been sent from you.