- Letter mail is between 5" and 11.5" long, 3.5" to 6.125" high, 0.007" to 0.25" thick, and not more than 3.5 ounces in weight.
- Flat mail is between 11.5" and 15" long, 6.125" and 12" high, 0.25" to 0.75" thick, and not more than 13 ounces in weight.
- Card mail is a subcategory of letter mail with physical dimensions of between 5" and 6" long, 3.5" and 4.25" high, and 7 points to 0.25" thick. What your customers call a postcard could, depending on its size, be either a card or a letter. For example, a postcard measuring 4.25x6" is considered a card, while a postcard measuring 5.5x8.5" is considered letter mail.
Here is a tip about thickness: 7 point stock or a sheet of 20-pound bond that is trifolded will meet the minimum requirements. However, these are both so thin that the mail piece could arrive looking battered. Instead of meeting the minimum, select stock that is thick enough to travel well through the mail stream—at least 9 points for card stock and 60-pound offset for trifolds.
Determining Postage: The Address Panel
The address panel of a mail piece includes the return address, the indicia, and space for the outbound address and barcode. It also could include these optional elements: postal endorsements (tells the USPS what to do with mail that is undeliverable as addressed), teaser copy, and graphics.
The size of the address panel is important. It needs to be wide enough to comfortably contain the longest line in the outbound address, tall enough to comfortably contain the number of address lines (usually three or four, but sometimes more), as well as the postal coding lines (usually two) and barcode. At a minimum, make the address panel 2" high and 4.125" wide, but allow more room when possible.
For flat mail being mailed at the standard mail rate, locate the address panel in the upper half of the mail piece. This requirement applies both to envelopes and self-mailers, such as newsletters. It does not apply to flat mail being mailed at the first class presort rate, but to keep it simple, use the upper half of the mail piece for any flat.
For letter mail, locate the address panel 0.5" from the right edge and 0.625" (5/8") inch from the bottom of the mail piece. (The USPS designates the bottom 5/8" of the mail piece as a clear zone that must be free of all writing or graphics.) If you add the minimum dimensions of the address panel to the dimension from the right and bottom edges of the mail piece, then the minimum size for an address panel (measured from the right side and bottom edge of the mail piece) is 4.625" wide by 2.625" high.
Locate the indicia in the upper right corner and the return address in the upper left corner. Be sure that the last line of the return address is at least 2.75" from the bottom edge of the mail piece. Any lower and it will be in the MLOCR (multi-line optical character reader) clear area, which could result in the return address being confused with the outbound address and the mail mistakenly delivered back to the return address.
For a folded, unbound, letter size self-mailer, orient the address panel so the fold is at the bottom. Most self-mailers with a bottom fold require only one wafer seal (or tab).
Keep the area where the outbound address will appear clear of graphic design. Avoid any background or use a very faint screen. If the mail piece is a flood print, whether it is a solid ink color or a graphic element, knock out the area for the outbound address. The MLOCR requires good contrast between the background and the outbound address; insufficient contrast may render the mail piece not mailable at the best postage rates.
Here are two tips for the address panel: It does not have to be the entire face of an envelope or self-mailer, nor the entire right half of a postcard. It can have a landscape orientation (that is, parallel with the longest edge) to qualify as letter mail, even if the mail piece itself has a portrait orientation.
Recommending Paper and Coatings
When recommending the paper for a mail piece, make sure it is thick enough (at least 9 point), has sufficient flexibility to make the turns around the belts, rollers, conveyor wheels and drums of the USPS high speed mail processing equipment, and has sufficient opacity that printing on one side won’t show through to the address panel. Avoid stocks with patterns or dark fibers, fluorescent colors, and synthetic papers unless you know the mail house can address on synthetics (very few can).
Aqueous and UV coatings provide a special challenge for inkjet addressing—each requires a special ink formulary and a dryer to cure the ink. Before applying an aqueous or UV coating after printing, check to be sure the mail house can address on the coating.