Sender Policy Framework

MAAWG published a revised version of their Sender Best Communication Practices

The Messaging Anti-Abuse Workining Group stated in their 2008-06-02 BCP (PDF): "At the very least, senders should incorporate SPF records for their mailing mailing domains".

MAAWG paper about e-mail authentication

In a paper published by the MAAWG in March 2008 Dave Crocker explains the technical background of SMTP e-mail authentication, and the protocols DKIM, SPF, and Sender ID: Trust in Email Begins with Authentication (PDF).