Sender Policy Framework, or SPF, is a validation system, that is intended to prevent the so-called e-mail spoofing where an email message can be sent from one e-mail address, but to seem as being sent from a different, usually with the objective to scam the recipient someway. If 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 globally have it. The record features all of the mail servers that are allowed to send valid messages from an address within the domain. When an e-mail is sent, the first DNS server it encounters verifies the SPF record and when its sending server is permitted, the message is sent to the target receiver. If, however, the sending server doesn't exist in the SPF record for the specified domain, the message will not be submitted and it'll be removed. Whenever you use this solution, it will stop third parties from sending spam that look as if they have been sent by you.