Tried another way. Removed entries from /ets/hosts and added them to the local server. Added to default relay: mнdomain.com. Disabled lookup MX: no
nslookup mydomain.com
mydomain.com MX preference = 10, mail exchanger = mail.mydomain.com
mail.mydomain.com internet address = 192.168.0.4
mail.mydomain.com internet address = 192.168.0.230
Mail arrives randomly to one of the two servers