"Email on the Internet can be forged in a number of ways. In particular@ existing protocols place no restriction on what a sending host can use as the ""MAIL FROM"" of a message or the domain given on the SMTP HELO/EHLO commands. This document describes version 1 of the Sender Policy Framework (SPF) protocol@ whereby ADministrative Management Domains (ADMDs) can explicitly authorize the hosts that are allowed to use their domain names@ and a receiving host can check such authorization."