Why Taxonomy Design Beats Model Choice in Email Classification

The true key to email classification isn't model selection—it's taxonomy design. When you structure your labels around specific actions (reply within 1 hour, reply today, no reply needed, archive) rather than topics, even lightweight models achieve high accuracy and can run autonomously at scale. This insight reframes how teams build email agents, shifting focus from prompt engineering and model obsession to the foundational architecture that actually drives system performance and reliability.