environment passed from sendmail?

(Posted a few days ago in comp.mail.sendmail, no reaction.)

Hi.  I haven't administered sendmail myself in a long time; ever since I
adopted Debian as my preferred OS, I have used their default MTA, which
was first smail, then exim; so excuse me if this question is nooby.  But
my mail does pass through a server running sendmail [call it S] on its
way to me, and not being root on $S I can't quite dig in and investigate
myself.

I use procmail to forward my mail from $S to my personal server.  I
believe this is enabled with the feature_local_procmail configuration
macro (not sure of spelling).  In any case, I don't have a .forward
file, only a .procmailrc.  Now I'd like to do some tricky things with
procmail and it would help to have some info from the MTA (example: the
envelope sender and recipient, and the sendmail local id of the
message).  Is there a way for sendmail to pass these items to procmail
in the environment, and if so is it on by default on the sendmail side?
[1] 

I can't test that just by invoking env or printenv from procmail,
because procmail discards almost all of the environment unless it's
started with the -p flag, and I think the way sendmail invokes procmail
on $S is without -p.

If it turns out that sendmail does pass such environment items but
procmail discards them, would it help to bypass the direct procmail
delivery and use a .forward file instead, with the line

 |/usr/bin/procmail -p /home/me/.hidden_procmailrc

IOW, would sendmail still pass the env items to a pipe delivery running
from within a .forward?

Thanks for any ideas.

[1] 
Exim, for example, passes the SENDER, RECIPIENT, and MESSAGE_ID
environment variables to any pipe delivery, either those invoked from
.forward files or configured directly in exim.

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