The
developers
of
SpamAssassin,
who have taken giant leaps forward in developing and
integrating various spam filtering techniques into a
sophisticated heuristics-based tool.
A lot of smart people who developed the excellent Exim MTA, including: Philip
Hazel <ph10 (at) cus.cam.ac.uk>, the
maintainer; Tom Kistner <tom (at)
duncanthrax.net>, who wrote the Exiscan-ACL patch
for SMTP-time content checks; Andreas Metzler
<ametzler (at) debian.org>, who did a really
good job of building the Exim 4 Debian packages.
Many, many others who contributed ideas, software, and
other techniques to counter the spam epidemic.
You, for reading this document and your interest in
reclaiming e-mail as a useful communication tool