[Exim] expansion of acl message-modifier

Hello,

which expansion variables can I use for the acl deny
message? My users tend to send one mail to several
recipients. If it fails they get
"550 unknown user" or
"550 unroutable address".
Of course they like to know then, which address failed.
In the moment I have to look up every time which one
has failed in the exim logfile.
I tried to put $recipients in the message text, but got
an expansion-error in the log.
It should come out like this:
"550 unknown user (michael.patschull@???)"
Would be great if someone had me a short hint!

Thanks,
Michael
 /*****************************************************
Michael Patschull              Heinrich Klumpp GmbH
michael.patschull@???
                               Motorstrasse 59
                               D-70499 Stuttgart
                               Tel: ++49-711-86707- 0
                               Fax: ++49-711-86707-13
                               www: www.klumpp.de
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