[Exim] Missing delivery failure message and duplicate e-mail…

Hi,

I've inheritted a mail system using Exim (3.22)
and Amavis (version Perl-11) on a SuSE 7.3 machine.

The references to Amavis in the Exim runtime
configuration file is correct, as far as I can see
from the installation instructions.

amavis_router:
    condition = "${if eq {$received_protocol}{scanned-ok} {0}{1}}"
    driver = domainlist
    route_list = "*"
    transport = amavis

amavis_director:
    condition = "${if or {{eq {$sender_address_domain}{<our domain>}} {eq {$received_protocol}{scanned-ok}}} {0}{1}}"
    driver = smartuser
    transport = amavis
    #unseen

Everything seemed to work OK until we realised that
we are not getting delivery failure messages if we
send an e-mail to an unknown domain.

If I add 'unseen' to the amavis_director section,
we do get the delivery failure messages. The problem
then is that all incoming messages are duplicated.

Any suggestions as to what we are doing wrong?

Thanks

Isabel