SPF, which abbreviates Sender Policy Framework, is a certification system that aims at protecting against the so-called email faking. Essentially, this indicates sending a message from one e-mail address and making it look like it’s sent from another with the idea to scam in some way the person receiving it. In case the SPF protection is active for a domain name, a record which has all of the mail servers authorized to email messages with addresses part of the domain is created. The record is stored on all of the DNS servers that route the web traffic globally, thus they all will recognize whether an email message originates from a valid server or not. The check is performed at the first server where the e-mail goes through and in the first case the e-mail message is forwarded, but in the second one it's removed and it never reaches the supposed recipient. Employing SPF records for your domains will prevent all unauthorized people from making use of your emails for malicious objectives.