Productivity gurus have produced four books, a manifesto and eleven newsletters on reaching inbox zero, which is why their inboxes are full.
Skip the methodology. Open a brand-new email address: it arrives at zero, factory-fresh, no filters or folder taxonomy required. The old inbox still holds 14,306 unread messages, but that is the old you’s problem — you are now a person with a clean slate and, briefly, no correspondence of any kind. Repeat annually, or whenever the number comes back.