Dossiers: the matter, not the folder
Folders describe where something is stored. A dossier describes what it is about. That is the difference between filing and an overview.
What a dossier is
A dossier is the bracket around a matter: a building site, a client, a dispute, a project. Inside are messages from several threads, the attachments, the appointments that came out of them and your notes. Messages from different senders belong there too, as long as they concern the same thing.
The autopilot files new messages into the right dossier by itself when the connection is unambiguous. Where it is unsure, it asks.
Archive instead of delete
Finished dossiers move to the archive. They leave the daily view but stay fully searchable. That matters, because the one message you need years later is always the one you thought was unimportant at the time.
For retention duties that means: nothing is lost just because you tidied up.
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Keep reading
Arriving mail is grouped by kind and urgency before you ever see it.
A draft in the right language and the tone you configured, ready to edit.
A morning summary with the open items pulled out of it.
Proposed times from mail land in the calendar, linked back to the message.