[Exim] Diagnosing transport failures

Hi.. I'm fairly new to Exim and am currently running v4.20 on OS-X along
with Maildrop.. I'm finding that I get a fair amount of messages in my
/var/log/exim_mainlog that look like the following :

2003-06-09 10:55:31 HG874I-0001SG-DD == my_email@??? R=maildrop
T=maildrop_pipe defer (0): Child process of maildrop_pipe transport
returned 75 (could mean temporary error) from command:
/usr/courier-imap/bin/maildrop

What I've found is that they are likely from one of the following :

1) A .cshrc that has naughty stty commands being issued for a
non-interactive session
2) Something wrong in the ~/.mailfilter file..

Is there any possible way to have what Maildrop is complaining about (or
any other output for that matter) to be fed back into Exim to be added to
the log when such an error occurs?

This makes it fairly difficult to diagnose these sorts of issues without
finding an offending message to manually "feed" into maildrop to see what
it is complaining about.. Is there some FAQ item I missed?

TIA!

-- Rick