bobsmith@gmail.com - email used to register on zoho a.k.a. super admin's account email

bob@smith.com - domain email

For some reason bob@smith.com is tied to bobsmith@gmail.com. When looking at the user details, it shows it like so.

I don't get why there is one of my domain emails tied to my super admin account. On top of that I can't change/remove that default email. I don't want a mail account for the super admin account.

This is extremely confusing because when opening zoho mail. It'll say "Loading... bobsmith@gmail.com", but show all the emails from bob@smith.com. Under the mail accounts under mail administration in the zoho control panel, it'll show bob@smith.com, but has the profile pic of bobsmith@gmail.com. Then under user details, it shows bobsmith@gmail.com with an mailbox address of bob@smith.com.