[Exim] why no Subject line in log

I get the Subject line in the Exim Mainlog in one configuration of Exim,
but not the other.

Both versions are running Exim 3.16.

The relevant configuration settings to get the Subject line in the log seem
to be

log_level = 3
log_queue_run_level = 5
log_subject

My log entry says

2000-10-19 17:25:56 13mJS0-0002Lp-00 <=
directors-admin@??? U=discuss P=local S=2236
id=00b801c039f0$b8954b20$f6b01b3f@GTEpamchef from
<directors-admin@???> for directors


And I am expecting the Subject to appear after the for clause. This is
coming from a mailing list, with the following director

discuss_aliases:
driver = forwardfile
file_transport = address_file
pipe_transport = address_pipe
reply_transport = address_reply
require_files = /home/ftp/discuss/${local_part}/dist
file = /home/ftp/discuss/${local_part}/dist
no_check_local_user
forbid_pipe
forbid_file
modemask = 002
one_time
skip_syntax_errors
syntax_errors_to = syntax



Any suggestions on other relevant configuration settings that I may have
mis set ?

Thanks

mark