SPF, which abbreviates Sender Policy Framework, is a certification system that aims at blocking the so-called e-mail forging. In simple terms, this means sending some message from one email address and making it look like it’s sent from another with the idea to scam in some way the person receiving it. In case the SPF protection is activated for a domain, a record that includes all of the mail servers authorized to send messages with addresses in the domain is generated. The record is saved on all the DNS servers that direct the web traffic worldwide, so that they all will identify whether an e-mail message comes from a valid server or not. The verification is conducted at the very first server where the email goes through and in the first case the email message is forwarded, while in the second one it is discarded and it never reaches the intended recipient. Using SPF records for your domains will prevent all unwanted people from making use of your emails for malicious purposes.