[exim] reverse dns check

Ive been using this

deny    message = inconsistent or no DNS reverse entry for
$sender_host_address
         !sender_domains =
/usr/local/etc/exim/whitelisted-domains
         !authenticated = *
         condition = ${if eq{$host_lookup_failed}{1} {1}{0}}

which I picked up off the list and its been working well for dropping
lots of spam but ive also had the odd false positive like this one

2009-04-30 14:26:20 [4717] H=(clearview01.clearviewdns.net)
[69.56.235.170]:2835 I=[94.76.221.176]:25 F=<nic@???>
rejected RCPT <alf@???>: inconsistent or no DNS reverse entry
for 69.56.235.170

Is there a better way of doing this ?

Thanks
Terry