mailbox.cloudmail.ondemand.com has no NS records.
NS records for this zone are defined at cloudmail.ondemand.com.
NS records for this zone are defined at cloudmail.ondemand.com.
Question and response
Question
dig mailbox.cloudmail.ondemand.com. NS
Answer
The response has no answer records.
Authority
cloudmail.ondemand.com. 7200 SOA ns1.sap.net. dns.sap-ag.de. 2019030348 3524 600 3600000 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0