This continues our series of introductory posts on designing for direct mail. Part 1 introduced your friend at the post office, the Mailpiece Design Analyst, the basic mailpiece shapes, and some helpful online resources. Here in Part 2, we'll look more closely at the shapes and other ways that the USPS categorizes mail.

Factors determining the type of mailing
As a designer, unless the format of the mailpiece and the class of mail are already decided for you, you'll be basing decisions about the design of the piece on what kind of message, information, or material needs to be conveyed, weighed against how much the client is willing to pay to get their piece into the hands of the recipients on their list. This cost analysis tool can help start that decision-making process if the client is unfamiliar with commercial mailing.

Retail or Discount
In most cases, commercial mail is discount mail and is designed for easier processing by the post office's equipment. Not meeting the specific physical requirements will bump you back up to full retail price or incur a nonmachinable surcharge. Retail is synonymous with Full Rate First Class. There is also a discounted Presorted First Class category for commercial mailings. 

Size and Shape of Mailpiece
As mentioned in Part 1, any piece of mail will be classified as a postcard, letter, flat, or parcel, depending on the dimensions of the piece.

Postcard
Small postcards only
To qualify for the postcard rate:

Letter
Larger postcards, letters, booklets, self-mailers

*Maximum length for a letter will be 10-1/2 inches effective 9/8/09.

Flat
Larger envelopes, newsletters, magazines, larger booklets, larger self-mailers

*Maximum length for a letter will be 10-1/2 inches effective 9/8/09.

Parcel
Anything that isn't a postcard, letter, or flat

Class
Classes can be thought of as service levels. The class affects postage rates, speed, and services included such as forwarding and returning.

Express Mail

Anything mailable can be sent Express

First Class Mail
Anything mailable can be sent First Class

Standard Mail
Advertisements, circulars, newsletters, magazines, small parcels, merchandise

Periodicals
Newsletters, magazines

Package Services
Merchandise, books, circulars, catalogs, computer-readable media, film, recordings, educational materials, binders, other printed matter

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In Part 3, we'll look at what you need to know to get your mailpiece through the USPS's processing equipment.