SPF, which means Sender Policy Framework, is an email safety system, that is used to verify if an email message was sent by a licensed server. Employing SPF protection for a given domain name will prevent the counterfeiting of emails created with the domain. In simple words: activating this attribute for a domain makes a special record in the Domain Name System (DNS) that contains the IP of the servers that are allowed to send e-mails from mail boxes under the domain. Once this record propagates globally, it exists on all the DNS servers that direct the Internet traffic. Whenever some email message is sent, the initial DNS server it goes through verifies if it originates from an approved server. If it does, it is sent to the destination address, however if it doesn't originate from a server indexed in the SPF record for the particular domain, it is rejected. Thus nobody can mask an email address and make it appear as if you're distributing spam messages. This technique is also referred to as email spoofing.