Note that in this last set of examples you were using the systemd resolver (127.0.0.53). Which might be setup (or not) to query the bind server you are testing.
I suggest to always start from a clean slate in that case. You can clear the systemd resolver cache by running: sudo systemd-resolve --flush-caches Another interesting check, if you keep using that resolver, is systemd- resolve --status -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1787739 Title: postfix name lookup failed after dist-upgrade (Aug-2018) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/bind9/+bug/1787739/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs