Postage Rates 2024 Flat Envelope Mail. Explore the usps postage rate shifts for postcards, flats, and letter sizes in 2024, and. Shipstation offers affordable usps postage thanks to our close relationship with usps postage provider stamps.com.

 — the regular flat rate envelope will be priced at $9.85 , with the legal size and padded flat rate envelopes priced at $10. Overall, priority mail prices will increase 5.7 percent.