[exim] Recipient verification at ACL - alias checking

Hi All,

Using Exim 4.63-17

I'm trying to setup recipient verification at the acl stage,
specifically 30_exim4-config_check_rcpt in the split config file setup.

I have a postgres lookup that works fine, only problem being I have a
few aliases in a flat text file that also need to be checked. I have
been trying lsearch as follows

deny
   message    = No such user
   !acl        = acl_whitelist_local_deny
   domains    = domain.com
   !local_parts = ${lookup{$local_parts}lsearch{/etc/exim4/aliases}}
   log_message = "DENIED: No such user"

I have tried a couple of variations, one with just local_parts instead
of $local_parts. but they all seem to get bypassed and a 'DENIED: No
such user" logged. All mail that has a user in the pgdb works fine.

help appreciated

Regards,
Mark