Sender Policy Framework, or SPF, is a verification system, which is employed to prevent the so-called email spoofing where an e-mail message is sent from one email address, but to seem as being sent from another one, often with the objective to fraud the recipient for some reason. When SPF protection is enabled for a domain name, a special record is created for it in the Domain Name System and all DNS servers worldwide have it. The record contains all the e-mail servers that are allowed to send valid messages from an email address under the domain. When a message 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 destination. When, however, the sending server doesn't exist in the SPF record for the given domain, the e-mail message won't be submitted and it'll be removed. Whenever you employ this service, it'll stop third parties from sending spam which look as if they have been sent by you.