@Sanjeev thanks, will be useful deleting already processed ticket as in OsTicket.
This is very useful when you manage more than one email of support and manage it directly from the ticket system.
Not deleting email is consuming inbox space also is causing issue on ticket deletion.
Also create issue if you need to migrate else way or if you delete ticket this will create a ticket created again for operator and customer.
Hope you will be able to provide a solution for delete email once processed.