mx.ptd.net has no NS records.
NS records for this zone are defined at ptd.net.
NS records for this zone are defined at ptd.net.
Question and response
Question
dig mx.ptd.net. NS
Answer
The response has no answer records.
Authority
ptd.net. 3600 SOA dns1.ptd.net. etoybrg.corp.ptd.net. 2025062501 10800 3600 604800 10800
Additional
. 0 OPT ; payload 512, xrcode 0, version 0, flags 0