From their site: Integrate a variety of USPS Web Tools into your website, shipping operation, or customer service center - for no additional fee. Our Application Program Interfaces (APIs) provide U.S. Postal Service rates, shipping labels and much more while keeping your customers on your Web site.
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There are no source code libraries or how-to links for US Postal Service. If you know one why not add it?
mail is not being delivered916457-6043