Where in exim.conf is this located? It should be in the WHM > Exim Configuration Editor > Advanced Editor area under routers section. If it isn't the routers section, it likely won't work properly.
Here is what precedes the box where it should be listed:
Code:
######################################################################
# ROUTERS CONFIGURATION #
# Specifies how remote addresses are handled #
######################################################################
# ORDER DOES MATTER #
# A remote address is passed to each in turn until it is accepted. #
######################################################################
# Remote addresses are those with a domain that does not match any item
# in the "local_domains" setting above.
#
# Demo Safety Router
#
democheck:
driver = redirect
require_files = "+/etc/demouids"
condition = "${if eq {${lookup {$originator_uid} lsearch {/etc/demouids} {$value}}}{}{false}{true}}"
allow_fail
data = :fail: demo accounts are not permitted to relay email