[secure]

Try any DNS name which only has a AAAA record, e.g. ipv6.google.com, which results in “An unexpected error occurred.”

[sajagi]

Alright, thanks!

[snvzz]

As an added note, your server seems to resolve some A record, despite no A records in the domain. I suspect whatever you're using for DNS does park all NXDOMAIN into some website of their own.

[snvzz]

As secure explained.