mx.frcesc.com has no NS records.
NS records for this zone are defined at frcesc.com.
NS records for this zone are defined at frcesc.com.
Question and response
Question
dig mx.frcesc.com. NS
Answer
The response has no answer records.
Authority
frcesc.com. 3600 SOA dns.frcesc.com. hostmaster.frcesc.com. 1771773771 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0