We need a DNS expert for a DNS problem. We run Ubuntu 16.04. We have migrated DNS Bind9 to a new server in the cloud. But each time we disable BInd9 on the original local server, DNS and outside email stops working. DNS will no longer point to ns1.our.domain or mail.our.domain on the new Bind9 server. If we fire up Bind9 on the original local server, all works again.
DNS files seem to be correct, we have been running our own DNS server for 10 years. There is something, somewhere that we cannot figure out. We are looking for an expert that can use dig and other such tools to solve the problem.