Quoting Craig Sanders (cas@taz.net.au):
might have been me. i don't recall reading or hearing of it before I started doing it, or before i started mentioning it as a useful anti-spam technique.
of course, it's something so simple and obvious that it's likely to have been independently invented several times.
Which is true of most truly inspired ideas: They're obvious and elegant, after you hear and admire them. Sysadminly judo at its finest. Antispam is an area that exposes a common computerist flaw: Lack of perspective and a tendency to energetically focus on solving the wrong problem -- which in turn produces tactical mistakes like C-R software, huge / slow / buggy Perl regexes, and elaborate schemes to conceal e-mail addresses. It's rare to see a thoughtful balance.