Filtering Non-existant User Accounts

Hi.  This might be the same question as before, but I think
the list did not receive it.

How do you use procmail to filter all the spam which goes
to 'names' which do not exist?

The only place I can think of in sendmail R0 rule-set; but
when I try it, it does not work.

Could someone who had done this reply (privately is okay).

Thanks!

-- 
   Tim Bass
   Principal Consulting Engineer
   Tel: (703) 222-4243
   Fax: (703) 222-7320
   EMail: bass(_at_)silkroad(_dot_)com
   http://www.silkroad.com/