How to set up 2 mail servers on the same domain?

Question

Exim

Hello. Faced such a problem. You need to set up Yandex.Mail and mail on the server with ISPmanager 5 Lite. Mail from Yandex works as it should, but mail on the server can only send letters to external servers. The DNS entries are:

TXT | @ | v=spf1 ip4:server_ip include:_spf.yandex.net ~all
MX | @ | mx.mydomain.ltd

In the ISPmanager 5 Lite panel itself, in the incoming and outgoing mail server settings section, there is an address mail.mydomain.ltd . How can this address be changed to mx.mydomain.ltd? My domain is served on the Cloudflare DNS server and the mail.mydomain.ltd domain is proxied, which causes a conflict between A and MX records.