My reasons for not liking TMDA as a solution:
- Electronic mail was never designed to be "instant messaging". Depending on how the mail is handled, it can take 1-30 minutes (on a good day) for the message to be delivered. TMDA does not take into account firewalls, virus scanners, forwarders, etc.
- You want to to send another message to okay the one I just sent just so I can get on your whitelist? grrr...
- Once I'm on your whitelist, do I get kicked off when someone gets infected with Kazaa and the virus just loves my address when forging headers of infected messages.
- The technical level of the solution will confuse the majority of the people who use e-mail. In other words, it's not "transparent" and will probaby be avoided by people who have dial-ups and only use them for e-mailing out pictures of the grandkids. (This level of user vastly outnumbers the people who'd understand the use of TMDA.)(IMO)
Personally, I like spam-scoring and then sorting the flagged messages into a separate folder for manual deletion. Yeah, a few still get by the filters, but I don't lose that forwarded content that my Mom thought I'd find useful.