First Class Mail is the fastest option for delivery. Usually delivered 2-3 days locally and up to 4 days nationwide. First Class comes with mail forwarding and return to sender. Businesses also have the option to mail as Certified Mail.
If there are more than 500 pieces in a First Class mailing it can be presorted to receive a lower postage rate and receive the same benefits of First Class. To achieve a lower rate, the addresses have to be CASS/NCOA certified.
Marketing Mail is also known as "Standard mail". Each mailing has to have a minimum quantity of 200 pieces to qualify. This class is used for marketing mail such as postcards, letters, flyers, catalogs, and other advertising. Standard Mail is usually delivered locally within 3-6 business days. Nationally it can take 1-3 weeks.
Non Profit Mail has the lowest postage rate of all class of mail. Organizations have to be registered and authorized by the US Postal Service to mail at this rate. It is processed and delivered the same way as Marketing Mail.