mailhost.lightning.net has no NS records.
NS records for this zone are defined at lightning.net.
NS records for this zone are defined at lightning.net.
Question and response
Question
dig mailhost.lightning.net. NS
Answer
The response has no answer records.
Authority
lightning.net. 7200 SOA thunder.lightning.net. internic.lightning.net. 2021081600 3600 1800 604800 7200
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0