go
mx.mail.nl.uu.net, etrn.mail.nl.uu.net and fallback.mail.nl.uu.net are subdomains to this hostname. nl.uu.net is a domain controlled by three nameservers. All of them are on different IP networks. Incoming mail for nl.uu.net is handled by one mailserver having a total of two IP numbers. They are on the same IP network.

nl.uu.net
ns-soa records
ns.nl.net
+ 193.78.240.1 193.78.0.0/15 AS702 -
+ --- -
ns records
ns-sec.ripe.net
+ 193.0.0.196 193.0.0.0/21 AS3333 -
+ --- -
ns.nl.net
+ 193.78.240.1 193.78.0.0/15 AS702 -
auth60.ns.nl.uu.net
+ 193.67.79.134 193.67.0.0/16 AS702 -
mx records
emr.eu.uu.net
+ 195.129.12.211 195.129.0.0/16 AS702 emr0.eu.uu.net
+ --- emr0.eu.uu.net
+ 195.129.12.212 195.129.0.0/16 AS702 emr1.eu.uu.net
+ --- emr1.eu.uu.net
subdomains
etrn.mail.nl.uu.net
fallback.mail.nl.uu.net
mx.mail.nl.uu.net