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What is the USPS's thickness and weight limit for Automation and/or Machinable letters? MailStream Plus

Product affected: MailStream Plus™, all versions, all platforms
These limits for automation/machinable letters are from the USPS DMM (Domestic Mail manual) section 201, parts 1.0 and 3.0. (Non-machinable letters are in 2.0)
The section numbers and text are current as of May 2019.  
Other text in the DMM may also apply as to qualification for Automation or Machinable letters, and weight and thickness limits.

1.0 Physical Standards for Machinable Letters and Cards
1.1 Physical Standards for Machinable Letters
1.1.1 Dimensional Standards for Letters
Machinable letter-size mail is:

a. Not less than 5 inches long, 3-1/2 inches high, and 0.007-inch thick.
  1.  0.007 inch thick if no more than 4-1/4 inches high and 6 inches long; or
  2.  0.009 inch thick if more than 4-1/4 inches high or 6 inches long, or both.
b. Not more than 11-1/2 inches long, or more than 6-1/8 inches high, or greater than 1/4-inch thick.
c. Rectangular, with four square corners and parallel opposite sides. Letter-size, card-type mailpieces made of cardstock may have finished corners that do not exceed a radius of 0.125 inch (1/8 inch) unless prepared as Customized Market Mail under 243.9.0. See Exhibit 1.1.1.
d. Within an aspect ratio (length divided by height) of 1.3 to 2.5, inclusive. See 3.7.
e. Subject to additional dimensional restrictions in 3.0, depending on mailpiece design.

1.1.2  Weight Standards for Machinable Letters
The maximum weight for Presorted First-Class Mail machinable letters is 3.5 ounces (0.2188 pound). The maximum weight for USPS Marketing Mail machinable letters is 3.5 ounces (0.2188 pound).


3.0 Physical Standards for Machinable and Automation Letters and Cards
3.3 Dimensions and Shape

Each machinable or automation letter-sized piece must meet the dimensional standards in 1.1.1. Machinable or automation letter-sized pieces may be subject to additional dimensional restrictions in 3.0, depending on mailpiece design.

3.5 Maximum Weight, Machinable and Automation Letters and Cards
The following maximum weight limits apply:
a. Critical Mail letters - 3 ounces.
b. Booklets and unenveloped disc carriers - 3 ounces.
c. Machinable enveloped letters and cards - 3.3 ounces.
d. Automation enveloped letters and cards - 3.5 ounces (see 3.6 for pieces over 3 ounces.)
UPDATED:  May 16, 2019