SPF, which is an abbreviation for Sender Policy Framework, is a validation system that is aimed at preventing the so-called e-mail counterfeiting. Basically, this means sending a message from one e-mail and making it look like it’s sent from a different one with the idea to scam in some way the person opening it. If the SPF protection is active for a domain, a record which contains all mail servers authorized to email messages with addresses within the domain is generated. The record is stored on all DNS servers that route the web traffic around the world, so that they all will identify whether an email message originates from an authentic server or not. The verification is done at the very first server where the email goes through and in the first case the message is forwarded, while in the second it's discarded and it never reaches its intended recipient. Using SPF records for your domain names will stop all unauthorized people from using your emails for malicious purposes.