System-wide anti-spam .rc file

I'm beginning to think about a way to hook up some anti-spam .rc files
in such a way so that non-UNIX mail users could benefit.  Right now
more than half the company uses Lotus Notes, mail arrives at a UNIX
machine and is gatewayed into notes via an alias or $HOME/.forward
file.  I would like to filter such mail before it is forwarded to
Notes.  Another potential use for something like this would be setting
up a spam-filter remailer - (properly) forwarding your mail to
filterspam(_at_)somewhere(_dot_)org would do the filtering and then send the
message back to you.

Anyway...before I do too much, I thought I'd check to see if somebody
has already done something similar.  Note that I don't think using
"procmail" as the local delivery agent won't really help much, as mail
for Notes users just passes through the UNIX box (maybe I'm
wrong?).  Here's what I have in mind:
  # spam.rc
  #
  # Try to detect SPAM and take appropriate actions when found.
  #
  # This file is designed to be used from the /etc/aliases file to
  # filter mail destined for some other address.  Typical usages would
  # be as follows
  #   user: "| /path/to/procmail FILE=user FLAG=subject /this/file.rc"
  #   fwd: "| /path/to/procmail MAIL=fwd(_at_)host FLAG=discard /this/file.rc"
  #   prog: "| /path/to/procmail PIPE=/some/prog FLAG=header /this/file.rc"
  # The first option is [FILE|MAIL|PIPE], this determines what should be
  # done with messages that aren't spam (or flaged as SPAM).  The FLAG
  # variable determines what would be done with detected SPAM
  #   subject - modify the Subject line to indicate SPAM was found
  #   discard - send the message to /dev/null
  #   header - add an X-This-Is-Spam: header to the message
  #
Is there an easier/better way?  (The above disables any existing
$HOME/.forward file).

Thanks in advance for any comments or suggestions.
   Dan
------------------- message is author's opinion only ------------------
J. Daniel Smith <DanS(_at_)bristol(_dot_)com>        
http://www.bristol.com/~DanS
Bristol Technology B.V.                   +31 33 450 50 50, ...51 (FAX)
Amersfoort, The Netherlands               {info,jobs}(_at_)bristol(_dot_)com