As long as you have access to the old email address, you should be able the change that email address. You can add a second email address and confirm this email address. Once it has been confirmed, you can make the second email address your primary email address. *https://support.mozilla.org/en-US/kb/change-primary-email-address-firefox-accounts *https://support.mozilla.org/en-US/kb/add-secondary-email-address-firefox-accounts