This DNS issue appears to have been rectified.

Our Server administrators are currently investigating reports that our Domainz Cloud DNS records are not resolving correctly for some customers. This will only affect certain customers whose domains are pointed to the below nameservers: ns1.nsserver.net.nz ns2.nsserver.net.nz ns3.nsserver.net.nz Affected customers may experience their websites failing to load, and incoming mail may be delayed or may bounce back to senders.