Hi,
I tried to host my own www server and now, I am trying to host my own email server too!
Here is what I want to do and like to know what should I set in dynu's control panel as well as servers.

mydomain.net = serverA
mail.mydomain.net = serverB
both domain were dynamic DNS

under mydomain.net:
*.mydomain.net and www.mydomain.net with record A, and I saw IP address that is the public IP of serverA

under mail.mydomain.net
*.mail.mydomain.net having A and AAAA record, and the public IP of serverB was correctly reported.

However, I never can go directly to mail.mydomain.net, when I visit it, it always go to serverA. I am guessing if it is serverA's setup?

Both servers were setup with Ubuntu 18.04.

Appreciate if anyone can help!
Kent