Your deleted emails will remain in your Trash until the end of time. If you delete an email from the Trash, it will be gone forever.
Similarly, unshared files and folders you delete from Drive will remain in your Drive trash forever. At this time, there is no way to permanently delete files and folders from the Drive trash.
Note that shared folders cannot be deleted; they are instead removed from your My PreVeil view in the browser and unsynced from your local devices.
To recover a deleted file or folder, you will need to download it from the Trash and then re-upload it to your Drive.