> People at my site including myself keep receiving junk-advertising.

> How can I force 'sendmail' to bounce/disconnect/fail in some way that
> the remote machine gets an error, or at least make it send the mail
> to /dev/null ?

The easiest way to send it to /dev/null is to have your MTA accept it
and then drop it on the floor.  Bouncing it is rarely going to help,
because the bounce will bounce and land in your local postmaster's
mailbox anyway - identifying a useful address to bounce it to is
_hard_, probably AI-complete.  (The only address that's easy to
generate is postmaster on the machine talking to you, but that machine
is probably an innocent intermediate hop, not guilty at all.)

The basic hard problem is _identifying_ spam mail mechanically - and
doing so in a way that simultaneously picks up enough of it to be worth
doing without discarding any significant fraction of non-spam mail.

Personally, I just send complaints to postmaster and domain contact
addresses (the latter obtained from WHOIS).  So far I've seen very few
repeat offenses (ie, I've rarely had occasion to complain about a
single address or site more than once).  In my case, I'm lucky when it
comes to identifying spams - there's an address that has been out of
date for years but is still accepted by our mailer, and forwarded to
me.  This address _never_ receives legitimate mail; I've not seen
anything but ad-spams mailed to it for multiple years.  It must be on
some popular-among-spammers list of addresses....

					der Mouse

			       mouse@rodents.montreal.qc.ca
		     7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B