SPF, which abbreviates Sender Policy Framework, is a validation system that is aimed at blocking the so-called email counterfeiting. In simple terms, this means sending some message from one e-mail 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 running for a domain, a record that includes all of the mail servers authorized to send messages with addresses part of the domain is generated. The record is placed on all the DNS servers that route the Internet traffic around the world, so they all can recognize if an email message originates from a trustworthy server or not. The verification is conducted at the very first server where the email goes through and in the first case the e-mail message is forwarded, and in the second it is removed and it never gets to its intended recipient. Using SPF records for your domain names will prevent all unauthorized people from making use of your email addresses for malicious purposes.