Please follow these steps to deactivate the auto-renewal for the mailbox:
- In your account go to PRODUCTS > EMAIL.
- In the list of domains, click on the "View" icon to the right of the concerned domain and then on MANAGE to the right of the concerned mailbox.
- Set the "Mailbox auto-renew" option to OFF.
IMPORTANT: If you deactivate the auto-renewal option, you will have to renew it manually before the expiration date to avoid permanently loosing all of your mailbox's contents.