Sender Policy Framework, or SPF, is a validation system, which is used to prevent the so-called email spoofing where an e-mail message is sent from one address, but to appear as being sent from another, ordinarily with the objective to fraud the recipient someway. If SPF protection is enabled for a domain, an exclusive record is made for it in the Domain Name System and all DNS servers worldwide get it. The record features all of the email servers that are permitted to send valid messages from an address part of the domain. When an email is sent, the first DNS server it encounters checks the SPF record and when the sending server is authorized, the message is forwarded to the target receiver. If, however, the sending server is not included in the SPF record for the given domain, the message will not be sent and it will be removed. If you use this solution, it'll stop third parties from sending spam e-mails that look as if they have been sent from you.