Sender Policy Framework, or SPF, is a verification system, which is intended to prevent the so-called email spoofing where an e-mail message is sent from one email, but to look as being sent from a different one, generally with the idea to fraud the recipient for some reason. When SPF protection is activated for a domain name, a special record is created for it in the Domain Name System and all DNS servers worldwide get it. The record contains all the e-mail servers that are allowed to send valid messages from an address part of the domain. When an email is sent, the very first DNS server it encounters verifies the SPF record and in case its sending server is authorized, the message is sent to the targeted destination. If, however, the sending server doesn't exist in the SPF record for the particular domain, the e-mail message will not be sent and it'll be discarded. Whenever you employ this service, it will prevent third parties from sending spam messages that seem to have been sent from you.