mx.kiubi.com has no NS records.
NS records for this zone are defined at kiubi.com.
NS records for this zone are defined at kiubi.com.
Question and response
Question
dig mx.kiubi.com. NS
Answer
The response has no answer records.
Authority
kiubi.com. 300 SOA ns1.amen.fr. root.amen.fr. 2026020402 86400 7200 2592000 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0