Bulk mail preparation

Volume of mailing

There must be a minimum of 200 pieces or 50 pounds to qualify for a bulk mailing. Every mail piece must be identical.


Zip codes are required on every address. Missing zip codes will delay your mail. Only pieces sent to a U.S. address may be included. International mail may not be mixed with domestic bulk mail. Check our list of states, possessions, and territories if you are unsure.

The sending department’s full return address is required on each mail piece. Postal Service-approved University of Iowa return addresses are posted on this website and published in the UI directory (herd book). An improper return address will not be accepted by the Postal Service.


Mail pieces must be sorted in ascending zip-code order. Mark boxes or trays indicating the order. For example, write “1 of 5”, “2 of 5”, and so forth, if you have five boxes of mail.

Bar code

All letter-size reply cards and envelopes (business reply, courtesy reply, and metered reply) enclosed in a bulk mailing must bear a correct delivery-point bar code for the address to which the mail piece is to be returned.


Tabs made of paper or light plastic must be used to close self-mailers. Mailing Service has equipment that places tabs according to postal standards. Staples will disqualify your mailing for a discount.


Endorsements indicate what the sender wants the Post Office to do with mail pieces that are undeliverable as addressed. Endorsements must have a minimum 8-point type size, stand out clearly against the background, and have a 1/4-inch clear space above, below, and on both sides.

They must be located below the return address, immediately above the delivery address, and either left of the postage area and below any rate marking or below the postage area and rate marking.

Indicia/permit imprint

A block of text indicating that postage has been paid must be printed or imprinted by a meter on each mail piece.

Permit 45

UI Mailing Services holds this U.S. Postal Service permit to send bulk mail and maintains an account with the Postal Service to pay the postage due on the permit. All University departments are eligible to use permit #45; contact Mailing Services for permission to do so. Do not deliver your permit mail to the Post Office. It must go through Mailing Service to have the proper forms signed and submitted.

Permit 844

is used for business reply envelopes or cards. The appropriate facing identification marks (FIM), bar code, horizontal bars, and nine-digit zip code must be correctly positioned on the card or envelope. Mailing Services provides a Postal Service template to use for positioning.

The first line of the address must be The University of Iowa and the second line must include the departmental account that will be charged for the use of permit 844.

The zip code for permit 844 is always 52240 plus four digits, which vary depending on whether the piece is a card or an envelope, or if it weighs more than one ounce.

Paper and ink

Use dark ink on light paper for high contrast. Light-colored ink on dark stock and fluorescent paper and ink may not be machine readable.

Size and shape

Items smaller than the minimums are not mailable. Items larger than the maximums are termed flats and cost more to mail. Postcards and letters must be rectangular with an aspect ratio (length divided by height) between 1 to 1.3 and 1 to 2.5 to qualify for letter rates.
  • Letter size

    Minimum 5” wide x 3-1/2” high, .007” thick; maximum 11-1/2” wide x 6-1/8” high, .25” thick
  • Flat size

    Minimum 11-1/2” wide x 6-1/8” high, .25” thick; maximum 15” wide x 12” high, .75” thick
  • Postcard

    Minimum 5” wide x 3-1/2” high, .007” thick; maximum 4-1/4” wide x 6” high


The weight limit on a nonprofit letter is 3.2873 ounces (0.2055 lbs.), the regular rate letter weight limit is 3.3087 ounces (0.2068 lbs.). Pieces over these weight limits are mailable at the higher rate for flats.

UI Mailing Services
178 Mossman Business Services Bldg
Iowa City, Iowa 52242-1602
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