The USPS (United States Postal Service) is a federal agency responsible for providing shipping and mailing services to the United States. Its origin dates back to the late 18th century when Benjamin Franklin was the postmaster general. The USPS is only one of a few agencies explicitly authorized by the constitution; it is legally obligated to serve all Americans at uniform price and quality.
The prices mentioned above vary from class to class, though. Mail Classes were created to give citizens the option to pay more for faster delivery, or higher quality, of a particular package or piece of mail. Mail classes also have weight restrictions, so you may be obligated to choose from a smaller range of class options if you are shipping a package over a certain weight. The following chart outlines the current domestic mail class structure:
| Class of Mail | Speed | Low Cost |
| Priority Mail Express | Yes | No |
| Priority Mail | Yes | yes |
| First-Class Mail | Yes | yes |
| USPS Marketing Mail | No | yes |
| Periodicals | Yes | yes |
| Package Services/USPS Retail Ground | No | yes |
| Class of Mail | Speed | Low Cost |
Priority Mail Express
Priority Mail Express is the fastest mail service offered by the USPS. It provides guaranteed 1-2 day services for any mailable matter. Packaging for this class is also free at your local post office.
Priority Mail
Priority Mail is considered the best “value” when factoring in speed + costs. Some mail must be sent as Priority Mail such as Bills, Statements, or credit cards.
First-Class Mail
First class mail prices are the same regardless of how far the mail travels. Many beginning mailers use this class because it is the most simple. You simply put a stamp on your single piece of mail and drop it in a mailbox.
USPS Marketing Mail
Not required to be mailed as first-class mail or a periodical, marketing mail prices are bulk prices and the quantity of mail must be a minimum of 200 pieces of mail or weight at least 50 pounds.
Periodicals
This class of mail is designed specifically for newspapers, magazines, and other publications that are sending mail to subscribers or requesters. Periodicals must be published and mailed at least four times a year on regular intervals.
Package Services/USPS Retail Ground
Package service is an umbrella term for three classes of different mail which are Bound Printed Matter, Media Mail, and Library mail. Packaged services mail do not receive expedited service.
