SPF, which stands for Sender Policy Framework, is an email security system, which is employed to verify whether an e-mail message is sent by an authorized server. Employing SPF protection for a domain name will prevent the counterfeiting of email addresses created with the domain. In simple words: activating this function for a domain name creates a special record in the Domain Name System (DNS) which contains the IP of the servers that are allowed to send email messages from mailboxes under the domain. The moment this record propagates globally, it exists on all the DNS servers that route the Internet traffic. Every time an email message is sent, the initial DNS server it goes through tests if it comes from an approved server. When it does, it's sent to the destination address, but when it doesn't come from a server listed in the SPF record for the particular domain, it is rejected. In this way nobody will mask an e-mail address to make it look as if you are e-mailing spam messages. This technique is also called email spoofing.