Sender Policy Framework, or SPF, is a verification system, that is designed to prevent the so-called e-mail spoofing where an e-mail message is sent from one e-mail address, but to look as being sent from another one, ordinarily with the idea to scam the recipient for some reason. If SPF protection is enabled for a domain name, an exclusive record is made for it in the Domain Name System and all DNS servers around the world get it. The record contains all e-mail servers that are permitted to send valid messages from an e-mail address within the domain. When an email is sent, the very first DNS server it encounters checks the SPF record and in case its sending server is authorized, the message is forwarded to the targeted receiver. When, however, the sending server doesn't exist in the SPF record for the given domain, the e-mail message will not be submitted and it will be discarded. When you use this service, it'll stop third parties from sending spam which look as if they have been sent by you.