i just deployed new bind-9.6.0-p1 and I'm getting a lot of these:
May 5 20:18:41 dd named[21037]: host unreachable resolving '128.235.241.88.zen.spamhaus.org/TXT/IN': 2001:7b8:3:1f:0:2:53:1#53 _______________________________________________ bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
