mail.xinet.com.mx has no NS records.
NS records for this zone are defined at xinet.com.mx.
NS records for this zone are defined at xinet.com.mx.
Question and response
Question
dig mail.xinet.com.mx. NS
Answer
The response has no answer records.
Authority
xinet.com.mx. 180 SOA ns20.digicertdns.com. dns.digicertdns.com. 2009010563 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0