usps priority express mail rates are based on package weight, dimensions, and delivery zone. Flat rate options start at around $28, while variable rates depend on specifics like destination and volume. This premium USPS service offers overnight delivery with tracking and insurance included. Commercial users can access discounted rates through shipping software or volume contracts. It’s especially beneficial for businesses needing urgent delivery of documents or high-value goods. Accurate labeling and meeting daily cutoff times are necessary to guarantee the overnight delivery promise.