Sender Policy Framework, or SPF, is a validation system, which is intended to stop the so-called email spoofing where an email message is sent from one e-mail address, but to look as being sent from a different one, often with the objective to fraud the recipient someway. When SPF protection is activated for a domain name, a specific record is generated for it in the Domain Name System and all the DNS servers around the world receive it. The record includes all e-mail servers that are permitted to send authentic messages from an e-mail address part of the domain. When an email is sent, the very first DNS server it encounters checks the SPF record and in case the sending server is authorized, the message is forwarded to the targeted receiver. If, however, the sending server doesn't exist in the SPF record for the particular domain, the e-mail message will not be forwarded and it'll be discarded. In case you employ this solution, it'll prevent third parties from sending spam which look as if they have been sent by you.