How to make multiple MX records for a domain?

Question

Mail server

Good afternoon.
I have 2 lines from 2 operators, the traffic is balanced. There is an internal mail server (exchange), an external domain with 1 mx-record (it resolves to the isp1 address). Tell me, how to tie the second ip-address to the same record more correctly and painlessly, or is it more correct to do it through a separate mx-record with its own name (subdomain) and do redirects?
Thanks in advance to those who respond)

Answer 1

A domain has several MX records with different priorities. In the following, the records themselves are described.

nodomain.ru.       IN      A       1.2.3.4
                        IN      MX      10      mx
                        IN      MX      20      mx2
mx                   IN      A       1.3.5.7
mx2                 IN      A       1.2.5.9

The first mail will be received by IP 1.3.5.7. If it is not available, it will accept IP 1.2.5.9.