Sender Policy Framework, or SPF, is a validation system, which is designed to prevent the so-called e-mail spoofing where an e-mail message can be sent from one email, but to seem as being sent from another, typically with the objective to fraud the recipient in some way. When SPF protection is activated for a domain, a unique record is created for it in the Domain Name System and all DNS servers worldwide have it. The record includes all mail servers that are permitted to send legitimate messages from an address part of the domain. When an e-mail is sent, the first DNS server it encounters verifies the SPF record and when its sending server is authorized, the message is forwarded to the target receiver. If, however, the sending server is not present in the SPF record for the specified domain, the email message will not be sent and it'll be removed. If you employ this solution, it'll stop third parties from sending spam that appear to have been sent by you.