[Exim] IPv6 newbie: suggestions sought

I've recently gotten an IPv6 tunnel. I've rebuilt Exim with IPv6
support. It all seems to work. I need to see if I have some UK money
laying around, to supply to a colleague attending this next course, for
the purchase of alcohol for Mr Hazel. :^) Thanks.

I'm looking through my config, looking for things that could do with
tweaking. Exim 3.36 (I'm a coward).

The most obvious thing is ignore_target_hosts on my Routers. Does
anyone know if there are address ranges which really should be forcibly
denied, that Exim doesn't avoid? I'm assuming that an attempt to open a
stream connection to a multicast address will fail, so that's already
handled. But what else?

Are there other options which I would be well advised to review?
"localhost" resolution includes ::1 so receiver_unqualified_hosts should
be okay.

Pointers gratefully received,
--
The code was willing,
It considered your request,
But the chips were weak.