mx.post.lu has no NS records.
NS records for this zone are defined at post.lu.
NS records for this zone are defined at post.lu.
Question and response
Question
dig mx.post.lu. NS
Answer
The response has no answer records.
Authority
post.lu. 300 SOA ns2.pt.lu. hostmaster.ns1.pt.lu. 2026021901 10000 1800 2419200 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0