SPF, which abbreviates Sender Policy Framework, is a certification system that aims at preventing the so-called email forging. Essentially, it indicates sending a message from one e-mail and making it look like it’s sent from another one with the purpose to scam in some way the individual opening it. If the SPF protection is running for a domain, a record which contains all of the mail servers authorized to email messages with addresses under the domain is generated. The record is placed on all DNS servers that route the web traffic globally, therefore they all will recognize whether an e-mail message originates from a legitimate server or not. The check is done at the first server where the e-mail goes through and in the first case the message is forwarded, but in the second one it's discarded and it never reaches its intended recipient. Employing SPF records for your domain names will stop all unauthorized people from using your emails for harmful objectives.