[exim] No route to host for sesame.csx.cam.ac.uk?

I just got a strange message in my mainlog when mailing to the
exim-users list:

2005-01-07 14:45:12 1Cn02g-0000Ki-7d sesame.csx.cam.ac.uk
[2001:630:200:8080:20e:cff:fe09:a58a]: No route to host

I suspect that this is because sesame has an AAAA record in DNS, and
exim is compiled/configured to use IPv6, but my host doesn't actually
have an IPv6-capable connection to the internet. Is that correct?

If so, is the correct solution "dns_ipv4_lookup = *" ?

Thanks,
- Marc