Mine

exim 4.63

local_delivery:
  driver = appendfile
  delivery_date_add
  envelope_to_add
  maildir_use_size_file
  maildir_format
  group = mail
  mode = 0660
  return_path_add
  directory = /home/$local_part/mail

My smarthost router;

smarthost_brain:
  driver = manualroute
  domains = ! +local_domains
  transport = remote_smtp
  route_list = * smtp.brain.net.pk randomize bydns

exim's daemon restarted, so that means so far the syntax is correct. Testing in/out mails..