SPF, which is short for Sender Policy Framework, is an e-mail safety system, that is used to confirm if an e-mail message was sent by an authorized server. Using SPF protection for a given domain will prevent the faking of email addresses made with the domain. In layman's terms: activating this feature for a domain name makes a particular record in the Domain Name System (DNS) which includes the IP of the servers which are permitted to send e-mail messages from mailboxes under the domain. Once this record propagates worldwide, it will exist on all DNS servers that route the Internet traffic. Every time an email message is sent, the initial DNS server it uses checks if it originates from an authorized server. When it does, it is sent to the destination address, however if it doesn't come from a server indexed in the SPF record for the domain, it is rejected. Thus nobody will be able to mask an email address and make it appear as if you're distributing spam. This method is also termed email spoofing.