remove primary email address

remove primary email address

I want to remove my "primary email address".

I have successfully been able to change it - but i'm not able to remove it. 

In my Calendar - it uses this "primary address" field to assign values to "Created by" or "modified by" or "Event organizer".   When i create events and invite other people - it sends an email to this primary address.

I just want bp1002@zoho.com to be the only account my calendar cares about. 

I don't understand why an external account is needed to manage my calendar.