[Exim] stripmime with exim/mailman

I'm using exim-3.34 with mailman 2.0.6 and attempting to pipe
messages through stripmime.pl before they go out to a
mailinglist. I'm not using /etc/aliases, instead have a
transport specifically for each list, works nicely. If I have
the following in exim's system filter:

# for testing
if $header_to contains "mailinglist"
then
   pipe /usr/local/bin/stripmime.pl
      seen finish
endif

...and I have this in exim's configure:

message_filter_pipe_transport = stripmime_pipe

...where stripmime_pipe is:

address_pipe:
driver = pipe
return_fail_output

...it fails with:

2002-03-28 13:51:42 16qho6-0000rK-00 original recipients ignored (message_filter)
2002-03-28 13:51:42 16qho6-0000rK-00 => |/usr/local/bin/stripmime.pl <message filter> T=stripmime_pipe

something I don't understand about the pipe no doubt.
thanks. --Rob

--
Rob Lingelbach                          http://www.alegria.com
Sysadm, Computer Animation Lab            rob@???
California Institute of the Arts           caltech@???