[Exim] how to set address_data in a dedicated router

Hi,

for a number of routers, I would like to set address_data to the uid
of a local user, so that I can use the uid in a precondition. I tried
it with this router:

set_address_data_uid:
  debug_print = "R: set_address_data for $local_part@$domain"
  address_data = "${extract{2} \
                           {:} \
                           {${lookup passwd{$local_part}}} \
                           {$value} \
                           {} \
                    }"
  driver = redirect
  data = :blackhole:
  unseen

But despite the unseen option being set, during actual message
delivery the message is blackholed, and not processed by other routers
any more.

What am I doing wrong here? Is a redirect to a blackhole really the
most elegant solution? Or can I have a no-op router more elegantly?

Any hints will be appreciated.

Greetings
Marc

--
-------------------------------------- !! No courtesy copies, please !! -----
Marc Haber          |   " Questions are the         | Mailadresse im Header
Karlsruhe, Germany  |     Beginning of Wisdom "     | Fon: *49 721 966 32 15
Nordisch by Nature  | Lt. Worf, TNG "Rightful Heir" | Fax: *49 721 966 31 29