Andrew Wheadon writes:
> 
> 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 ?

Good resources with specific sendmail.cf code and other stuff:

  Sendmail Home Page
    http://www.sendmail.org/ 

  Fight Spam on the Internet!
    http://www.cix.net/spam/ 

-bmw