SPF, which means Sender Policy Framework, is an email security system, which is used to validate if an email message is sent by an authorized server. Employing SPF protection for a particular domain will stop the counterfeiting of emails generated with the domain. In simple words: activating this feature for a domain name makes a specific record in the Domain Name System (DNS) which includes the IP addresses of the servers that are allowed to send e-mail messages from mailboxes using the domain. The moment this record propagates worldwide, it will exist on all DNS servers that direct the Internet traffic. Any time an e-mail message is sent, the first DNS server it goes through checks if it comes from an authorized server. When it does, it is sent to the destination address, however if it does not come from a server indexed in the SPF record for the particular domain, it is discarded. In this way nobody will mask an email address and make it look as if you're sending spam. This method is also called email spoofing.