SPF, which abbreviates Sender Policy Framework, is a certification system that aims at blocking the so-called e-mail counterfeiting. In simple terms, this means 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 opening it. When the SPF protection is activated for a domain, a record which includes all the mail servers authorized to email messages with addresses within the domain is generated. The record is placed on all the DNS servers that direct the Internet traffic all over the world, so that they all will identify whether an e-mail message comes from a trustworthy server or not. The check is performed at the first server where the email goes through and in the first case the message is forwarded, but in the second it is discarded and it never gets to the supposed recipient. Using SPF records for your domains will prevent any unauthorized people from making use of your emails for malicious purposes.