From the cPanel landing page, navigate to the 'Email' section. Now select the 'Track Delivery' button.
The first field you will see at the top is 'Recipient Email (optional)', which is a filtering option for the Delivery Report list. To see all present email delivery routes, press the 'Show All' button below. In the case of troubleshooting delivery errors, click the adjacent button 'Show Blocked & Failed'.
For the complete guide and list of term definitions, check out the official cPanel resource!