mx1.ip-only.net has no NS records.
NS records for this zone are defined at ip-only.net.
NS records for this zone are defined at ip-only.net.
Question and response
Question
dig mx1.ip-only.net. NS
Answer
The response has no answer records.
Authority
ip-only.net. 3600 SOA a.ns.ip-only.net. registry.ip-only.net. 2026021100 14400 3600 604800 3600
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0