smtp.sendingbox.net has no NS records.
NS records for this zone are defined at sendingbox.net.
NS records for this zone are defined at sendingbox.net.
Question and response
Question
dig smtp.sendingbox.net. NS
Answer
The response has no answer records.
Authority
sendingbox.net. 300 SOA x.ns.joker.com. hostmaster.joker.com. 2024110687 14400 3600 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0