[Exim] Rejection Explanation

I noticed this in my rejectlog:

----------------------------------------------------------------------------
--
2000-06-11 20:36:03 refused relay (host) to <user@???> from
<user@???> H=(marcus1) [62.x.x.x] (failed to find host
name from IP address)
----------------------------------------------------------------------------
--

I'm assuming that it can't resolve 62.x.x.x - 62.x.x.x does not have a
hostname associated with it - and is thus not accepting the message. Is
there a configuration option I can put in, to make exim accept messages in
this case? Are there any security implications in doing so?

Ollie