correo2.porta.net has no NS records.
NS records for this zone are defined at porta.net.
NS records for this zone are defined at porta.net.
Question and response
Question
dig correo2.porta.net. NS
Answer
The response has no answer records.
Authority
porta.net. 900 SOA dns1.porta.net. hostmaster.claro.com.ec. 374 28800 18000 604800 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0