f.mx.broadviewnet.net has no NS records.
NS records for this zone are defined at mx.broadviewnet.net.
NS records for this zone are defined at mx.broadviewnet.net.
Question and response
Question
dig f.mx.broadviewnet.net. NS
Answer
The response has no answer records.
Authority
mx.broadviewnet.net. 86400 SOA ns5-auth.windstream.net. hostmaster.windstream.net. 2020100600 28800 7200 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0