I have followed this tutorial to install mailcow: https://www.the-digital-life.com/mail-server-on-linux/
Now, when I visit: mail.mydomain.com, I see the same content as mydomain.com. I think there is something wrong with the DNS. See this: https://ibb.co/4YYf1yD
Mxtoolbox.com gives this error: Mail server failed to connect to SMTP server, and there is a problem getting the IP Address for the site.
Can you please advise on how can I get this work?