Configure primary company-DNS and additional mailinbox-DNS

Now company have 2 power-dns(pdns) servers and

In MailinBox have additional DNS server (ns3) is not PowerDNS.
How configured mailinbox DNS in this case? how update config?
I have opportunity disable MailinBox DNS and not use dns functionality(now namy error in “Check Status” about dns services)?

You can use existing DNS infrastructure to host the DNS for MIAB. Go to System -> External DNS for the records you’d need to enter into PowerDNS.

If you want to use MIAB as a mirror of the other two name servers, there is a DNS API documented in the Custom DNS page in the control panel that you can use to develop a solution.

I can disable DNS on mailinbox server?I have many error(about DNS) in status page because I am use two PowerDNS as Primary now.

This is currently not possible. Sorry.