DNS resolver sends empty reply to unsupported query
The Tor resolver sends an empty reply (status: NOERROR, QUERY: 1, ANSWER: 0) rather than an error when it does not support the type of the query (e.g. MX). This makes it impossible to setup a transparent torifying DNS proxy frontend that would ask Tor by default, and fallback to ttdnsd for DNS query types that are unsupported by the former.
Context: https://lists.torproject.org/pipermail/tor-talk/2011-June/020601.html