[Exim] callout problem

Ironically, while I was playing with verify.c someone @youpy.fr tried to
send a mail through my mailer, which has callout with random and
postmaster..

Exim was silly enough to believe youpy's MX record of 127.0.0.2--thank
goodness for its rate-limiting, otherwise it would have surely exploded!

I don't know what the right thing to do here is.. ..is it worth hacking
do_callout in verify.c to check it's actually going to connect to a
sensible IP address?

Matt