SPF, which stands for Sender Policy Framework, is an e-mail safety system, that is used to validate whether an e-mail message was sent by an authorized server. Employing SPF protection for a given domain will prevent the forging of email addresses generated with the domain. In simple words: enabling this attribute for a domain makes a specific record in the Domain Name System (DNS) which includes the IP addresses of the servers which are allowed to send email messages from mailboxes under the domain. As soon as this record propagates globally, it will exist on all the DNS servers that route the Internet traffic. Any time some email message is sent, the first DNS server it uses verifies if it originates from an authorized server. When it does, it is forwarded to the destination address, however if it does not originate from a server listed in the SPF record for the particular domain, it's discarded. In this way nobody can mask an e-mail address to make it look as if you are sending spam messages. This method is also called email spoofing.