William Leibzon wrote: But I really dont see how this would be any different then just logging with cgi, it'll result in positive logging for exactly same set of people. For example as I'm using PINE from unix shell, all those html images are not referenced in any way, nor are there requests set for them in dns.

Although this is true, the relevance of it is low. From the smart spammer's prospective, sending spam to people that use Pine makes no sense in the first place: people that use Pine are 1,000 times less gullible than the general population WRT to spam, therefore having their email addresses not confirm with cgi or whatever does not change the big scheme of things. I don't know about you, but the volume coming to my various "postmaster" or "administrator" is decreasing, as the ROI of spam sent to these must obviously be very low. In other words: if you're already to the point where you are using a text-mode mail client or disabling HTML and/or other stuff in a GUI client, you are no loss to the spammer if your email does not confirm as valid (because you would not even read it nor buy any of their crud in the first place).