Whatever you want to delete – any item type (email message, folder, IM contact ...) – just use drag ‘n’ drop. Drag the item onto the trash bin icon within the Navigation Pane and drop it when the icon becomes highlighted red.It is magic. Hold the CTRL key when dragging and dropping not to be asked to confirm deletion.

The main trash screen view:

Note: The difference between Trash and Recovery items is that Trash is available for email items only while Recovery Items is available only for groupware folders.