mx.cottonherrera.com has no NS records.
NS records for this zone are defined at cottonherrera.com.
NS records for this zone are defined at cottonherrera.com.
Question and response
Question
dig mx.cottonherrera.com. NS
Answer
The response has no answer records.
Authority
cottonherrera.com. 900 SOA ns-904.awsdns-49.net. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0