Sender Policy Framework, or SPF, is a verification system, which is designed to prevent the so-called email spoofing where an e-mail message can be sent from one email address, but to appear as being sent from another one, frequently with the purpose to fraud the recipient in some way. If SPF protection is activated for a domain, a unique record is made for it in the Domain Name System and all of the DNS servers around the world have it. The record contains all e-mail servers that are permitted to send authentic messages from an e-mail address under the domain. When an email is sent, the first DNS server it encounters verifies the SPF record and in case its sending server is authorized, the message is forwarded to the target receiver. When, however, the sending server is not contained in the SPF record for the given domain, the email message will not be submitted and it will be removed. In the event that you employ this solution, it will stop third parties from sending spam messages which seem to have been sent by you.