Scott Mace has a great interview on Opening Move with Scott Chaise.
I would recommend it to understand the current state of 'trusted' e-mail and open standards as they come out.

Finally, the war on spam is shifting to controlling outbound email traffic. This has profound implications for Internet service providers and for their customers. Zombie spambot attacks are being met with responses including blacklisting of users and entire ISPs. At Inbox-IT 2005 in San Jose, Scott Mace spoke with Scott Chasin, CTO of MX Logic, Inc. about efforts from Silicon Valley and Washington D.C. to control the spambots.

How can adoption rates be increased for SPF, Sender ID and DomainKeys? What role will the FTC's recently-released best practices recommendations for outbound email play? What are Port 25 blocking, subscriber reputation filtering, and acceptable use policies? What is the symbiotic relationship between service providers and the enterprise? How are enterprises liable for the spambot traffic they send out? What's the growing distinction between message submission vs. message transfer? What's the role of the IETF's RFC 2476? What is the challenge and opportunity that identity management poses for the messaging industry? Is SMTP broken? What are malicious opt-out attacks?