Most inboxes are not overflowing with email. They are overflowing with unmade decisions, sitting in a list that was never designed to hold them.
Three folders, not thirty
Everything that lands needs one of three answers: decide now, waiting on someone else, or done. Three folders hold that. Anything more granular than that is filing for its own sake.
The 12-minute version
Once a day, move every unread email into one of the three. Nothing gets answered during the sort — that is a separate pass. Separating triage from response is what makes the twelve minutes enough.
The inbox count stops mattering once it stops being where decisions live. It becomes a doorway again, not a to-do list.