Final answer:
A newsletter that weighs less than one pound falls under Second Class mail, which covers periodicals like magazines and newsletters published frequently. First Class mail is for correspondence, Third Class for marketing materials, and Fourth Class for heavy parcels.
Step-by-step explanation:
A newsletter that weighs less than one pound would be considered 'Second' class mail. The United States Postal Service (USPS) categorizes mail into various classes, each meant for different types of mail and services. Second Class mail (now known as Periodicals) is primarily used for magazines and newspapers, but also includes newsletters that are published at least four times a year. It's important to note that while weight does play a role in determining the class of mail, there are other factors, such as the frequency of publication and the purpose of the mailed items, that also influence this classification.
To clarify further, First Class mail is typically used for personal and business correspondence, bills, and cards, and is prioritized over other classes of mail in terms of delivery speed. Third Class mail (now known as Marketing Mail) is used for marketing, advertising, and promotional materials that are not time-sensitive. Fourth Class mail (now called Retail Ground) is used for packages and heavy parcels that don't require expedited shipping services.