Currently, SMS and fax email notifications for non-assigned/non-direct telephone numbers are emailed to the email address that is set in the RingCentral operator extension.
The only way to redirect those email notifications is to change the email addresses used by the operator's extension, or to add a specific extension to unassigned or non-direct (i.e. auto-attendant) telephone numbers. Both of these options are not ideal, as the operator may be using the extension and requires their own email address to remain the same for email notifications for SMSes and faxes sent to their specific extension, and also extensions would need to be assigned to telephone numbers unnecessarily.
It would be helpful to have administrator setting to direct SMS and fax email notifications that are received for unassigned/non-direct telephone numbers, or be able to direct those to a Group in RingCentral.