A postcard is a piece of thin cardboard or thick paper intended for writing and mailing without using an envelope. People use postcards to send messages and pictures to their loved ones anywhere. Postcards are also used by businesses to send messages to customers.
According to the United States Postal Service, postcards must be at least 3 1/2 inches high by 5 inches long by 0.007 inch thick and not more than 4 1/4 inches high by 6 inches long by 0.016 inch thick. Postcards are usually rectangular in shape. Thin postcards tend to get stuck in the mail processing system. It is important to talk to a mailpiece design analyst to help in designing the correct postcard size.