First-Class Mail (letters, postcards, and lightweight packages): typically delivered within about 1–5 business days after it’s accepted by the postal service. Delivery tends to be quicker for local or regional mail and longer for cross-country delivery.
Standard Mail (also known as Marketing Mail): this is a lower-cost service with no guaranteed delivery timeframe. It’s often used for bulk mailings, and delivery may take about 7–21 business days or longer, depending on volume and how far it needs to travel.
Keep in mind that these are estimated timeframes and actual delivery can vary based on distance, mail volume, holidays, weather, and other factors. If you need a specific estimate between ZIP codes, USPS tools are available to help calculate delivery windows.