[exim] No route to host - but msg sent successfully

HI,

I don't know why I got error "No route to host" when sending email to
the exim-users mailing list this morning, but the msg is sent
successfully as I can see it listed in the public now. I only get this
message after installed exim4.4 yesterday and leave it for overnight.
The error is;
2004-10-21 08:10:51 1CKQXX-00066D-L4 sesame.csx.cam.ac.uk
[2001:630:200:8080:20e:cff:fe09:a58a]: No route to host

Thanks
Sam