[exim] Rejecting non-existant users

Hi,

is use the exim as Mail Gateway with a Mailscanner to receive and send
my mails.
wen need splitted mail for spam checks because several user get all
mails other have a spam protection activated
To split the mails I use the follow Exim route settings:

split:
driver = accept
domains = *
condition = ${if eq {$received_protocol}{split}{no}{yes}}
transport = send_to_self
no_verify
no_more

now i want to use a text file that includes all existing users. Only for
this e-mail adresses exim should take the mails.
Additional all relay hosts shout be able to send mails to all recipient.

Can i define this in the router section or I need some acl ?

How I can do this ?

Thank's

Matthias