mx01.telus.net has no NS records.
NS records for this zone are defined at telus.net.
NS records for this zone are defined at telus.net.
Question and response
Question
dig mx.telus.net. NS
Answer
The response has no answer records.
Authority
telus.net. 3600 SOA dns24.telus.com. dnsadmin2.telus.com. 2018081064 900 7200 3600000 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0