correo.emtelco.com.co has no NS records.
NS records for this zone are defined at emtelco.com.co.
NS records for this zone are defined at emtelco.com.co.
Question and response
Question
dig emailemtelco.xinet.com.mx. NS
Answer
The response has no answer records.
Authority
xinet.com.mx. 180 SOA ns20.digicertdns.com. dns.digicertdns.com. 2009010566 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0