Sending to another domain on the same LAN

[goro]

Good day!
There are two different mail servers in one local network, one serves domain1.com, the second domain2.com.
How to tell the first server that sending mail to the second domain (domain2.com) should go to the local IP of the second server?

I tried to prescribe as described here
https://wiki.zimbra.com/wiki/Relay_per_Domain
but it’s not quite like that ...

[axslingr]

Setup an internal DNS server with your two domains as zones, point MX records to A records with private IPs of your servers.

Lance