How to properly configure a DNS server on a local network for a mail server?

Question

Domain Name System

Good afternoon.
I set up a mail server on iredmail, transferred letters from the yandex server using imapsync, forwarded ports, changed the priority of mx records on the external DNS server for the domain located on the Yandex server. Screenshot configuration. Through the web interface - roundcube everything works as it should. But for users in the local using the mail client it works only if I register the server with the local ip in the hosts file, in this case the mail client works correctly, if not registered, then the letters are not sent, but they arrive properly. Obviously, instead of editing hosts, you need to specify the settings in the local DNS server, and configure DHCP so that this DNS is primary, but I don’t understand DNS at all.
Tell me what you need to add in dns and maybe I missed something else ???
Perhaps I missed something in the external DNS settings? There is a website on the local network, so don't be surprised to see extra lines in the dns server.

Answer 1

One way is to create an email.domain.ru zone and a zone file with something like the following configuration:

@     IN     SOA    dns.lan.	admin.mail.lan. (
  2016103010
  28800
  7200
  604800
  86400 )
  IN   NS		dns.lan.
  IN   A		192.168.1.250