Mailing 101: how your #10 envelopes should look and act like.

"There are specific standards for preparing barcoded letter-size mailpieces mailed at automation rates," states USPS's Memo to Mailers newsletter. "Even letters that are not barcoded deserve the benefits of automated processing."

Here are some guidelines exerpted from the newsletter for making your mail readable and easier and cheaper to process.

* Choose colors carefully. Automated machines prefer plain white or light pastel backgrounds with addresses printed in dark colored ink. Dark or black paper envelopes result in an inability of sorting machines to read the address or barcode.

Bright or fluorescent colors on envelopes should be avoided due to their tendency to render cancelling machines unable to detect the front of the envelope.

* Font facts. USPS machines speak many "languages," but some fonts work better than others. The best font for readability is one using a sans serif format such as Arial or Helvetica. For best results, avoid italics, scripts, fonts with serif format, or stylized fonts. Condensed and bold fonts also cause the characters to crunch together and should be avoided.

* Through thick and thin. Letter-size pieces have to be at least .007 inches thick and are processed more reliably if they are .009 inches thick. The thickness maximum for letters is .25 inches.

The maximum letter-size is 6.125 high by 11.5 inches long.

* Avoid shifting in your windows. Sometimes the address shifts inside the envelope and moves out of the window. It's best to keep the address block 1/8 inch away from any edge of the window. The insert should fit snugly into the envelope so it does not shift in handling. The machines read addresses best through low-gloss type windows--polystyrene, cellophane and glassine all work well.

* Clear zone. When letters are not barcoded by the mailer, the Postal Service's optical-character readers attempt to apply it to the mailpiece.

The clear zone for such barcodes is a rectangular area at the lower right corner of the mailpiece that extends to the left 4.75 inches from the bottom right corner and 5/8 inches up from the bottom of the mailpiece. Keeping this area clear of any printing enables the application of a readable barcode.