[Exim] :fail: from a router

Hello all,

I am trying to add white and black listing for each individual virtual mail
user. Everything seems to be working with the exception of the text of the
failure notice. I have read 21.6 of the current spec which covers using
:fail:. Perhaps I am just mis-reading this section but the following router
should fail and return the specified error message:

blacklist_address:
driver = redirect
senders = ${lookup mysql{select sender_address from mail_blacklist_address
where domain_name = '$domain' and local_part = '$local_part' and
sender_address = '$sender_address' and list_action_on = 'yes'}{$value}}
allow_fail
data = :fail:$local_part@$domain has blacklisted all mail coming from
$sender_address

It does fail a blacklisted address but gives a different error message:

Hi. This is the qmail-send program at mail07a.vwh1.net.
I'm afraid I wasn't able to deliver your message to the following addresses.
This is a permanent error; I've given up. Sorry it didn't work out.

<lists@???>:
64.71.114.173 does not like recipient.
Remote host said: 550 unknown user
Giving up.


It's probably just me, but I appreciate any insight or guidance.

Thanks,
Lane