Hi JS, 

Welcome to Box Community and glad to assist! 

To change your email address, you should add it first as your secondary email. 

1. Log in to the Box website and navigate to your Account Settings. 


2. Scroll down to Login and Email Addresses, click Link Personal Email twice. 
   


3. Enter a valid email address.


4. 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.

For your reference, please see this article. 

Thanks for posting!