mail.ispsystem.net has no NS records.
NS records for this zone are defined at ispsystem.net.
NS records for this zone are defined at ispsystem.net.
Question and response
Question
dig mail.ispsystem.net. NS
Answer
The response has no answer records.
Authority
ispsystem.net. 900 SOA dns1.ispsystem.net. admin.ispsystem.com. 2026021608 7200 900 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0