Sender Policy Framework, or SPF, is a validation system, which is intended to prevent the so-called email spoofing where an e-mail message can be sent from one address, but to look as being sent from a different, ordinarily with the objective to fraud the recipient for some reason. If SPF protection is activated for a domain, an exclusive record is generated for it in the Domain Name System and all DNS servers worldwide receive it. The record contains all of the mail servers that are allowed to send authentic messages from an email address part of the domain. When a message is sent, the very first DNS server it goes to checks the SPF record and if the sending server is permitted, the message is sent to the target receiver. When, however, the sending server is not contained in the SPF record for the particular domain, the e-mail message won't be submitted and it will be discarded. If you use this solution, it will stop third parties from sending spam messages that appear to have been sent by you.