Hi there, 

Welcome to Box Community and glad to help!

To change your primary email address, you must start by adding it as your secondary email and here's the steps: 

• Login to box.com and navigate to your Account Settings


• In your Login and Email addresses section, click Add More Emails.
  


• Enter a valid email address.


• Click Save.

An email verification will be sent to the address you entered. Click the verification link in the email to confirm and add the alternate email to you account.

To make a secondary email address your primary email address:

• Click Make Primary next to the email address you want as your primary email address.

Hope it helps!