NOTIMP for unrecognized qtypes

[Jacob Hoffman-Andrews]

Hi all,

I'm trying to write some documentation for users of Let's Encrypt about
CAA. I believe it's the case that standards-conformant authoritative
resolvers should return NOERROR for qtypes they don't recognize, rather
than NOTIMP. Is this correct? If so, what is the relevant standard? I
haven't been able to find a citation in
https://tools.ietf.org/html/rfc3597,
https://tools.ietf.org/html/rfc6895, or https://tools.ietf.org/html/rfc1035.

Thanks,
Jacob