SPF, which stands for Sender Policy Framework, is an email safety system, which is designed to verify whether an e-mail message was sent by a licensed server. Using SPF protection for a given domain name will prevent the counterfeiting of email addresses generated with the domain. In simple words: activating this function for a domain generates a special record in the Domain Name System (DNS) containing 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 will exist on all DNS servers that direct the Internet traffic. When an email message is sent, the initial DNS server it goes through verifies whether it originates from an authorized server. If it does, it's forwarded to the destination address, yet if it does not originate from a server part of the SPF record for the particular domain, it is rejected. Thus nobody can mask an e-mail address and make it look as if you're distributing spam messages. This method is also known as email spoofing.