Sender Policy Framework, or SPF, is a validation system, that is employed to stop the so-called e-mail spoofing where an e-mail message can be sent from one e-mail, but to look as being sent from a different one, typically with the purpose to fraud the recipient in some way. If SPF protection is activated for a domain name, a specific record is created for it in the Domain Name System and all the DNS servers around the world have it. The record features all of the e-mail servers that are permitted to send valid messages from an e-mail address under the domain. When an email is sent, the very first DNS server it goes to checks the SPF record and in case its sending server is permitted, the message is forwarded to the targeted receiver. When, however, the sending server is not contained in the SPF record for the given domain, the email message won't be submitted and it will be removed. Whenever you use this solution, it will prevent third parties from sending spam which look as if they have been sent by you.