It would be a good UX if the Trash folder would disappear only when there are no deleted messages in it. If there are notes in the Trash, the folder would be visible. This will help the user to know when there are messages that need to be permanently deleted.
There was one topic a while ago that said “I have deleted 1500 notes from trash”, sometimes people are not aware that they have notes in trash.
This feature is on a really granular level (and for most people unnecessary), but still, it can be a nice touch.