This is one of Doug Otis's favorite rants, but I'll try to explain it in fewer than 54 paragraphs. *grin*

Today, all of our spam / not spam decisions are based on one or more of the following criteria:

• source IP address
• guesswork
• content comparison

Most of the time, any decisions made about the trustworthiness of the source IP address are based on guesswork too, but there just simply isn't anything else we can rely on about a message.

Politically and technically accurate (or close enough for a wide audience) -- very nice change after the rash of lame articles we've seen recently.

http://www.forbes.com/technology/2005/07/14/microsoft-yahoo-spam-cx_fr_0714spam.html?partner=rss

Building on discussions in Dusseldorf (and fitting nicely into some postings here), MAAWG has published a white paper titled "Important Considerations for Implementers of SPF and/or SenderID." A few selected quotes: