[Exim] Failing remote addresses with custom error messages

I'm using the following router from the Exim FAQ page under exim 3.36:

verify_check_specials:
  driver = domainlist
  condition = "\
    ${if eq {$local_part@$domain}{test@exampledomain}{yes}{no}}"
  verify_only
  fail_verify
  route_list = *

I'm blocking specific remote addresses (test@exampledomain is a valid
non-local address in my config). Now I want to customize the error
message that is received. Currently, the error that's received is:

550 Cannot route to <test@exampledomain>

How can I change that error? Is it even possible? I'd like to be able to
customize the error for each recipient (e.g., something like using
:fail: in an aliasfile).

Thanks,

Paul