mx.enviefacil.com.br has no NS records.
NS records for this zone are defined at enviefacil.com.br.
NS records for this zone are defined at enviefacil.com.br.
Question and response
Question
dig mx.enviefacil.com.br. NS
Answer
The response has no answer records.
Authority
enviefacil.com.br. 1800 SOA kim.ns.cloudflare.com. dns.cloudflare.com. 2396787894 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0