[exim] Bounce without detailed LMTP error?

Hello,

we are using the following lmtp transport to deliver messages:

mailbox_lmtpunix:
driver = lmtp
socket = /cyrus/config/socket/lmtp
batch_max = 20
user = cyrus
delivery_date_add
envelope_to_add
return_path_add

Sometimes an error occurs at the LMTP delivery so that log entries like
this occur in the mainlog:

2006-10-26 02:37:54 1GctFg-0001SP-6K ** test@??? R=mailbox_cyrus
T=mailbox_lmtpunix: LMTP error after RCPT TO:<test@???>: 552 5.2.2
Over quota

or also

2006-10-26 02:38:14 1GctG3-0001W9-M3 ** test@??? R=mailbox_cyrus
T=mailbox_lmtpunix: LMTP error after end of data: 554 5.6.0 Message
contains NUL characters

The failures are not exim's fault, but as the sender of such an email I
only get a bounce message without any hint on the problem that occured:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

test@???

------ This is a copy of the message, including all the headers. ------
[...]

How can I put the detailed LMTP-error into the bounce message? Otherwise
our users always have to forward the email to me, I have to look for an
according entry in the logfile and have to tell them what was going on.
That's very annoying.

Regards
Marten