Sender Policy Framework, or SPF, is a validation system, which is employed to prevent the so-called e-mail spoofing where an e-mail message can be sent from one e-mail address, but to look as being sent from another, typically with the objective to fraud the recipient for some reason. When SPF protection is activated for a domain name, an exclusive record is created for it in the Domain Name System and all the DNS servers worldwide have it. The record contains all the email servers that are allowed to send authentic messages from an address part of the domain. When a message is sent, the very first DNS server it encounters checks the SPF record and in case the sending server is permitted, the message is forwarded to the target receiver. When, however, the sending server doesn't exist in the SPF record for the particular domain, the email message won't be sent and it will be discarded. Whenever you use this solution, it will stop third parties from sending spam that seem to have been sent by you.