SPF, which is an abbreviation for Sender Policy Framework, is a validation system that aims at blocking the so-called email counterfeiting. Basically, it indicates 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 individual receiving it. In the event that the SPF protection is running for a domain, a record which includes all the mail servers authorized to send messages with addresses within the domain is created. The record is saved on all the DNS servers that direct the Internet traffic globally, therefore they all can identify if an email message comes from a trustworthy server or not. The verification is done 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 it is removed and it never reaches its intended recipient. Applying SPF records for your domains will prevent any unauthorized people from using your email addresses for harmful purposes.