mx03.usersonlnet.com has no NS records.
NS records for this zone are defined at usersonlnet.com.
NS records for this zone are defined at usersonlnet.com.
Question and response
Question
dig mx03.usersonlnet.com. NS
Answer
The response has no answer records.
Authority
usersonlnet.com. 300 SOA dns2.p07.nsone.net. domainadmin.firstdata.com. 763100756 1200 180 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0