Sender Policy Framework, or SPF, is a verification system, that is employed to prevent the so-called email spoofing where an email message is sent from one e-mail, but to seem as being sent from another, typically with the idea to fraud the recipient in some way. If SPF protection is activated for a domain, an exclusive record is generated for it in the Domain Name System and all of the DNS servers globally get it. The record contains all of the email servers that are permitted to send valid messages from an email address part of the domain. When a message is sent, the first DNS server it goes to verifies the SPF record and in case its sending server is authorized, the message is sent to the target destination. If, however, the sending server is not contained in the SPF record for the specified domain, the e-mail message will not be submitted and it will be removed. Whenever you use this service, it'll stop third parties from sending spam which appear to have been sent by you.