SPF, which is an acronym for Sender Policy Framework, is an email security system, which is used to verify whether an e-mail message was sent by a licensed server. Using SPF protection for a given domain will prevent the faking of emails created with the domain. In layman's terms: enabling this feature for a domain makes a particular record in the Domain Name System (DNS) which contains the IP of the servers that are permitted to send e-mail messages from mailboxes using the domain. When this record propagates globally, it exists on all of the DNS servers that route the Internet traffic. When a new email message is sent, the initial DNS server it uses checks if it comes from an accredited server. If it does, it is forwarded to the destination address, however when it doesn't come from a server indexed in the SPF record for the domain, it is discarded. Thus nobody will be able to mask an email address to make it look as if you're e-mailing spam. This technique is also identified as email spoofing.