Sender Policy Framework, or SPF, is a validation system, which is employed to stop the so-called email spoofing where an e-mail message can be sent from one e-mail, but to appear as being sent from another one, typically with the idea to scam the recipient someway. When SPF protection is enabled for a domain, a specific record is made for it in the Domain Name System and all DNS servers globally receive it. The record contains all of the e-mail servers that are allowed to send legitimate messages from an address within the domain. When an e-mail is sent, the very first DNS server it goes to checks the SPF record and in case its sending server is authorized, the message is sent to the targeted receiver. In case, however, the sending server doesn't exist in the SPF record for the specified domain, the email message will not be forwarded and it will be removed. In case you use this service, it will prevent third parties from sending spam messages that seem to have been sent by you.