mailaz-spf.terra.com.br has no NS records.
NS records for this zone are defined at terra.com.br.
NS records for this zone are defined at terra.com.br.
Question and response
Question
dig mailaz-spf.terra.com.br. NS
Answer
The response has no answer records.
Authority
terra.com.br. 720 SOA a.dns.terra.com. sysadm.terra.com.br. 2017046906 300 300 2419200 7200
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0