mx.rolbbit.com has no NS records.
NS records for this zone are defined at rolbbit.com.
NS records for this zone are defined at rolbbit.com.
Question and response
Question
dig mx.rolbbit.com. NS
Answer
The response has no answer records.
Authority
rolbbit.com. 3600 SOA dns.rolbbit.com. hostmaster.rolbbit.com. 1512789113 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0