mailbox.promoexpress.com.ec has no NS records.
NS records for this zone are defined at com.ec.
NS records for this zone are defined at com.ec.
Question and response
Question
dig mailbox.promoexpress.com.ec. NS
Answer
The response has no answer records.
Authority
com.ec. 300 SOA master.nic.ec. admin.nic.ec. 2026040241 600 600 2592000 3600
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0