I can't delete my first 'zoho email' after getting my own domain

I can't delete my first 'zoho email' after getting my own domain

I recently purchased my own domain and I have everything set up. I changed my default email to my new email using my own domain instead of @zoho but everytime I go to compose, it first shows the @zoho email first and i have to keep changing it in the 'from' section and I know eventually I'll forget to do it. I just want to delete that email completely but I can't figure out how