postfix: luser_relay [UNRESOLVED]

[plut0]

I was intending on setting up a general mailbox for mail to unknown users using the luser_relay variable in postfix. However, I noticed that mailbox_transport overrides it which I need for my setup. I also tried mailbox_command = /usr/bin/maildrop with luser_relay and now it is rejecting ldap users.

How exactly are you expected to use it? Is there another way around this?