ismtp.efolder.net.efolder.net has no NS records.
NS records for this zone are defined at efolder.net.
NS records for this zone are defined at efolder.net.
Question and response
Question
dig ismtp.efolder.net.efolder.net. NS
Answer
The response has no answer records.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0