Sender Policy Framework, or SPF, is a validation system, that is designed to prevent the so-called email spoofing where an e-mail message is sent from one email, but to appear as being sent from another one, generally with the idea to scam the recipient in some way. If SPF protection is enabled for a domain, a special record is created for it in the Domain Name System and all of the DNS servers worldwide have it. The record features all of the e-mail servers that are allowed to send legitimate messages from an address under the domain. When a message is sent, the very first DNS server it goes to verifies the SPF record and when the sending server is authorized, the message is forwarded to the target destination. If, however, the sending server is not present in the SPF record for the particular domain, the message won't be submitted and it'll be removed. When you use this solution, it will prevent third parties from sending spam messages which seem to have been sent by you.