[exim] Problem denying IPs in ACL that do not resolve to hos…

Hi,

I have a two gateway mail servers which scan and filter messages and then
pass
them onto exim on the terminating machines... I've applied the following
ACL to
on the terminating machines to stop them accepting any mail that isn't from
the
gateways or someone who has POP-before-SMTP'ed):

deny hosts = !my-gateway-mta-ip1 : !my-gateway-mta-ip2 :
!net-lsearch;/var/log/pop-ips.log
message = Please deliver the message via MX - not directly to this server!

It works sometimes - it blocked 82.253.73.79 (
lns-bzn-38-82-253-73-79.adsl.proxad.net)
from trying to send some viruses directly to the hostname but sometimes it
lets them
through (eg 203.154.117.2):

>>> host in "!my-gateway-mta-ip1 : !my-gateway-mta-ip2 :
!net-lsearch;/var/log/pop-ips.log"? no (failed to find host name for
203.154.117.2)
>>> deny: condition test failed
>>> processing "accept"

This is curious because I can find a hostname for that IP .... but
regardless how do I stop it
allowing by default?

Thanks,
Adrian.