Can't change my default email id

Can't change my default email id

Hi, I'm configuring my corporate ZBiz. I add my corporate mail to my account and changed the MX records.

Problem is that I can not see my corporate mail inbox, I just see zoho.com inbox and I already mark corporate Id as default email id.

How can I delete zoho.com account?
Why cant I see my corporate inbox?

thanks,

Andres