[exim] Recipient verification message

Hi

I want to reject mail, if the local recipient is invalid and I have the
following in my acl_rcpt:

  deny    message        = unknown user
          domains        = mydomain.de
          !verify        = recipient

However, exim printe "Unrouteable address" instread of "unknown user". Why?
Is there something I can do?

Regards,
Steffen