Sender Policy Framework, or SPF, is a verification system, which is designed to prevent the so-called email spoofing where an email message is sent from one address, but to seem as being sent from another one, typically with the objective to fraud the recipient for some reason. If SPF protection is enabled for a domain, a specific record is created for it in the Domain Name System and all the DNS servers worldwide get it. The record includes all the e-mail servers that are allowed to send legitimate messages from an address part of the domain. When an email is sent, the very first DNS server it encounters verifies the SPF record and in case its sending server is authorized, the message is forwarded to the target receiver. In case, however, the sending server is not included in the SPF record for the given domain, the email message won't be sent and it will be removed. When you employ this service, it will stop third parties from sending spam emails that seem to have been sent by you.