Incoming mail for tech.dbuzz.net is handled by one mailserver at mx.dbuzz.net. dbuzz.net share mailservers with this domain. dns-admin.tech.dbuzz.net are subdomains to this hostname. dbuzz.net is delegated to two nameservers, however one extra nameserver is listed in the zone. All nameservers are at dbuzz.net themselves. All of them are on different IP networks. Incoming mail for dbuzz.net is handled by one mailserver also at mx.dbuzz.net. dbuzz.net has one IP number.