Adding SPF to Your Anti-Spam Solution
Source: Network Box
The Sender Policy Framework (SPF) is an open standard that introduces a grammar for domains to describe the email they send. These descriptions are published in the Domain Name System (DNS), and Simple Mail Transfer Protocol (SMTP) receivers may use these descriptions to authenticate email and to better apply local policy. SPF also defines a designated sender scheme that domains can use to describe the hosts they send email through, and because SPF is extensible, other schemes can be added to the language.