mail.parktons.com has no NS records.
NS records for this zone are defined at parktons.com.
NS records for this zone are defined at parktons.com.
Question and response
Question
dig mail.parktons.com. NS
Answer
The response has no answer records.
Authority
parktons.com. 1800 SOA ns.gransy.com. root.gransy.com. 2772153729 86400 900 1209600 1800
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0