mx.grafinell.com has no NS records.
NS records for this zone are defined at grafinell.com.
NS records for this zone are defined at grafinell.com.
Question and response
Question
dig mx.grafinell.com. NS
Answer
The response has no answer records.
Authority
grafinell.com. 3600 SOA dns.grafinell.com. hostmaster.grafinell.com. 1591257097 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0