spfb.itesm.mx has no NS records.
NS records for this zone are defined at itesm.mx.
NS records for this zone are defined at itesm.mx.
Question and response
Question
dig spfb.itesm.mx. NS
Answer
The response has no answer records.
Authority
itesm.mx. 900 SOA ns1e.itesm.mx. please_set_email.absolutely.nowhere. 137 10800 3600 2419200 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0