SPF, which is an abbreviation for Sender Policy Framework, is an authentication system that aims at protecting against the so-called email counterfeiting. In simple terms, this indicates sending a message from one email address and making it look like it’s sent from a different one with the idea to scam in some manner the person receiving it. If the SPF protection is active for a domain, a record which has all mail servers authorized to send messages with addresses in the domain is created. The record is kept on all the DNS servers that route the Internet traffic all over the world, so that they all can recognize if an e-mail message comes from a trustworthy server or not. The check is done at the very first server where the e-mail goes through and in the first case the e-mail message is forwarded, while in the second it is removed and it never reaches its intended recipient. Using SPF records for your domain names will stop any unauthorized people from using your emails for malicious purposes.