Sender Policy Framework, or SPF, is a verification system, which is employed to prevent the so-called email spoofing where an email message is sent from one address, but to seem as being sent from another, generally with the idea to scam the recipient someway. When SPF protection is activated for a domain, a unique record is made for it in the Domain Name System and all the DNS servers globally receive it. The record features all of the mail servers that are permitted to send authentic messages from an email address within the domain. When an email 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 receiver. In case, however, the sending server is not present in the SPF record for the particular domain, the email message won't be submitted and it will be discarded. If you use this service, it will stop third parties from sending spam e-mails which seem to have been sent by you.