[Exim] Allowing connections from IPs

Hey all,

I've tried a couple different approaches, and have also searched the archives
as well as Google to no avail.

My goal is to allow incoming (not relay) mail from hosts who's IPs fail
lookup. Iunderstand the security issue, but it seems too many emails have been missed
or bounced back from other systems not correctly config'd. I've decided I'd
rather not miss those and take a risk instead. *sigh*

Example reject log message:

2002-03-15 11:24:37 recipients from [1.1.1.1] refused (failed to find host
name from IP address)

I'm running Exim 3.33 on Linux.

What options do I need to set to allow mail for users on my system from other
systems that fail DNS lookup?

Thanks all! Appreciate ANY input...

~C