In article <avvh6m$dbi$2$8300d...@news.demon.co.uk>,

Addresses are obviously (also) automatically harvested from
WWW-pages usings "crawlers".

Spam filtering can and is typically set at two levels, system-wide
and individual. For example all our university's incoming email is
screened with a black list. This eliminates part, but not nearly all
the spam, because the sieve cannot be made too tight, for obvious
reasons.

The second level is what the users do. Most don't know how to fight
it and succumb to just a daily deletion of spam from their
mailboxes. Having a modicum of programming skills, I have a balanced
combination of three measures which effectively has made my own
mailbox spamfree. The inner level of my system is a whitelist
allowing my associates and contacts to get through without further
ado. On the outer level I have a further black list of my own. These
two measures are not alone sufficient. The core of my system is an
email autoresponder (for users/hosts others than in those two
groups). It automatically sends (from a null address) back my
simple, public email password which all the other emailers are
required to use on the subject line in order to reach me. My system
employs procmail and Bourne shell scripts. The huge disadvantage is
that this system is too involved for a non-experienced user. Other
than that it is the only system that I know of that effectively
stops ALL spam at an individual's level. The spam usually comes from
forged addresses, so a spammer most often won't see my response, and
that's that. Furthermore, since spamming is typically a huge mass
activity, the spammers do not have the time nor the resources to
keep track of my public email password, even if they got the
autoresponse. For me this combined solution is a must, since being
active on the net, as I see from my logs, a lot of spam comes my
way. More on my solution at

Foiling Spam with an Email Password System
http://www.uwasa.fi/~ts/info/spamfoil.html

Timo's procmail email filtering tips and recipes
http://www.uwasa.fi/~ts/info/proctips.html

   All the best, Timo

--
Prof. Timo Salmi ftp & http://garbo.uwasa.fi/ archives 193.166.120.5
Department of Accounting and Business Finance  ; University of Vaasa
mailto:t...@uwasa.fi <http://www.uwasa.fi/~ts/>  ; FIN-65101,  Finland
Timo's  FAQ  materials  at   http://www.uwasa.fi/~ts/http/tsfaq.html