correo.multianau.com has no NS records.
NS records for this zone are defined at multianau.com.
NS records for this zone are defined at multianau.com.
Question and response
Question
dig correo.multianau.com. NS
Answer
The response has no answer records.
Authority
multianau.com. 300 SOA dns21.servidoresdns.net. hostmaster.servidoresdns.net. 2011011968 21600 3600 2419200 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0