Hi Stephan, 

Welcome to Box Community and glad to assist! 

To change your primary email, you can begin by adding a secondary email and here's the steps: 

To add an email address:

• Login to box.com and navigate to your Account Settings> Login and email addresses
  

• 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!