AccuSpam wrote:
The answer is that AccuSpam does *NOT* require the sender to do anything in
order for the recipient to receive the message. This it is a Challenge Non
Response (CNR) system.
Okay, but the challenge is still sent, so it has the same nuisance/spam
factor as a PTYLM scheme.
The response is merely to check if the sender is a non-existent address (if it
bounces back).
You don't have to actually send mail to check that. Look into an MTA
feature called "callback verification" for an idea how this can be done.