While trying out our domains with dnsflagday.net, we found everything fine except for all connections timing out for ns12.zoneedit.com with IPv6. You publish a AAAA record for it; does the DNS server know it's supposed to be listening there?
(ns1, ns2, and ns14.zoneedit.com answer both IPv4 and IPv6, ns12.zoneedit.com only IPv4.)
(ns1, ns2, and ns14.zoneedit.com answer both IPv4 and IPv6, ns12.zoneedit.com only IPv4.)