SPF, which stands for Sender Policy Framework, is an email security system, which is employed to validate if an e-mail message is sent by a certified server. Using SPF protection for a domain will stop the counterfeiting of email addresses generated with the domain. In layman's terms: activating this attribute for a domain name makes a special record in the Domain Name System (DNS) containing the IP of the servers that are allowed to send emails from mailboxes using the domain. As soon as this record propagates globally, it exists on all the DNS servers that direct the Internet traffic. Every time an email message is sent, the initial DNS server it uses verifies whether it originates from an accredited server. When it does, it is forwarded to the destination address, but when it does not come from a server part of the SPF record for the particular domain, it's rejected. Thus nobody can mask an e-mail address then make it appear as if you're e-mailing spam. This method is also identified as email spoofing.
