SPF, which means Sender Policy Framework, is an e-mail protection system, which is is intended to verify whether an email message is sent by an authorized server. Employing SPF protection for a given domain name will stop the counterfeiting of email addresses generated with the domain. In simple words: enabling this function for a domain makes a specific record in the Domain Name System (DNS) which includes the IP addresses of the servers that are permitted to send emails from mail boxes using the domain. The moment this record propagates worldwide, it exists on all the DNS servers that route the Internet traffic. Any time some email message is sent, the first DNS server it goes through verifies whether it comes from an official server. If it does, it is forwarded to the destination address, yet if it does not come from a server part of the SPF record for the particular domain, it's rejected. Thus nobody can mask an email address then make it look as if you're sending spam messages. This technique is also referred to as email spoofing.