mail.optus.com.au has no NS records.
NS records for this zone are defined at optus.com.au.
NS records for this zone are defined at optus.com.au.
Question and response
Question
dig mail.optus.com.au. NS
Answer
The response has no answer records.
Authority
optus.com.au. 900 SOA dns0.optus.net.au. hostmaster.optus.net.au. 2026030213 28800 7200 1209600 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0