The curious case of esic.in DNS

A couple of weeks ago, at my $dayjob, we implemented a recursive resolver with RPZ in an enterprise network. After a few days, the customer got back to us with an issue - the DNS resolution of the domain esic.in failed with an NXDOMAIN response. After a cursory look at the problem, it became evident that esic.in resolved correctly but www.esic.in did not. The customer also reported that if they switched the resolver to 8.