Mailpieces are classified by shape and by the way they are prepared. These classifications are based on how efficiently mailpieces can be processed on Postal Service equipment. The Postal Service classifies letters and cards into one of three categories: machinable, nonmachinable, and automation.
If you prepare your letters and cards so that they have an accurate address and can be processed on Postal Service equipment, your mail is "machinable" and eligible for "presort" prices. Machinable mailpieces must meet specific standards, including size, shape, and weight.
Maximum weight: First-Class Mail, machinable letters and Standard Mail machinable letters: 3.3 ounces, Periodicals letters: 3.5 ounces.
Machinable letters must not meet any of the nonmachinable characteristics.
Examples of a nonmachinable letter include:
If your letter-size mailpiece is machinable and displays the correct Intelligent Mail barcode, you may qualify for lower, "automation" prices. A letter or card meets automation standards and qualifies for automation prices if it meets the specific addressing, barcoding, and design standards.
Shape: rectangular. Aspect ratio (length divided by height): 1.3 to 2.5
Length is the dimension parallel to the address as read.