The Trash folder is available for each application in your account. When you open the Trash folder from the application, only items for that application are displayed. But when you select Empty Trash from any application, items from all applications are deleted.
You can recover files from the Trash by opening the Trash folder, selecting the email messages to recover and moving them to another folder.
Messages left in the Trash may be automatically purged, in which case you cannot recover them.