[Exim] Feature Request: warn_unknown

Due to various political pressures (d**n customers :-), I've had to include
+allow_unknown to accept messages from customer's mail gateways with no
reverse IPs... However, I'd still like to know when this happens, or when an
IP/name pair doesn't match up (reverse lookup returns a.b.c.com, but
a.b.c.com doesn't forward lookup to same IP). Is there a way as Exim
currently stands to get this into the log? (I'm running 3.03). If not, I'd
like to request that +warn_unknown be added, same semantics and behavior as
+allow_unknown, but would generate similar logging messages as
+allow_unknown being off.