SPF, which abbreviates Sender Policy Framework, is a validation system that is aimed at preventing the so-called email counterfeiting. Essentially, this means sending some message from one e-mail address and making it seem to be sent from another one with the objective to scam in some way the person receiving it. If the SPF protection is running for a domain, a record which includes all mail servers authorized to send messages with addresses within the domain is generated. The record is kept on all the DNS servers that route the web traffic internationally, so that they all can recognize whether an e-mail message comes from a trustworthy server or not. The verification is done at the very first server where the e-mail goes through and in the first case the e-mail message is forwarded, and in the second it's removed and it never gets to the intended recipient. Employing SPF records for your domain names will prevent any unauthorized people from making use of your emails for harmful objectives.