mail.prontonet.net has no NS records.
NS records for this zone are defined at prontonet.net.
NS records for this zone are defined at prontonet.net.
Question and response
Question
dig mail.prontonet.net. NS
Answer
The response has no answer records.
Authority
prontonet.net. 900 SOA nsb.vtx1.net. fieldopadmin.vtx1.net. 37 10800 3600 2419200 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0