go
webmail.itelefonica.terra.com.br are subdomains to this hostname. terra.com.br is a domain controlled by two nameservers at terra.com.br themselves. They are on the same IP network. Incoming mail for terra.com.br is handled by one mailserver at terra.com. terra.com.br has one IP number.

terra.com.br
a records
 
+ 200.154.56.80 200.154.0.0/16 AS11706  
+ ---  
ns-soa records
 
+   AS?  
+ ---  
ns records
ns1.terra.com.br
+ 200.176.2.172 200.176.0.0/16 AS11706 dns-slave01-poa.terra.com.br
+ --- dns-slave01-poa.terra.com.br
ns2.terra.com.br
+ 200.176.2.173 200.176.0.0/16 AS11706 dns-slave02-poa.terra.com.br
+ --- dns-slave02-poa.terra.com.br
mx records
vip-us-br-mx.terra.com
+ 208.84.244.133 208.84.240.0/21 AS40260 -
+ --- -
subdomains
webmail.itelefonica.terra.com.br