Does anyone has an idea what happend to the “Anonymous Remailer”.

Some years ago, there was an active scene of remailers in order to post anonym into the UseNet or send mails without a sender.

As far as I know, there have even been technical solutions to problems like finding out whether someone is writing something based on traffic. I remember that there were even concepts for a kind of mailing list that worked in principle while respecting privacy.

Has this been developed further?