9091f516df3b45ae3ba357a3ed7e31.mail.outlook.com has no NS records.
NS records for this zone are defined at mail.outlook.com.
NS records for this zone are defined at mail.outlook.com.
Question and response
Question
dig 9091f516df3b45ae3ba357a3ed7e31.mail.outlook.com. NS
Answer
The response has no answer records.
Authority
mail.outlook.com. 300 SOA ns1-80.azure-dns.com. azuredns-hostmaster.microsoft.com. 1 3600 300 2419200 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0