Cajun Collection logo.

Going PostalTips on Mailing and the DMM100 for Customers

[retrieved from]

Going to the local post office is a sightseeing tour and a study in sociology, and this venture two or three times a week will get you some sightseeing and let you learn about people.

There is usually a line, and it travels like a snake and is slower than a centipede, especially since the postal service is claiming financial loss and closing earlier than ever.

All that aside, you may need to be a city lawyer to understand the DMM (Domestic Mail Manual). There is a guide for the common man called the DMM100: A Customer's Guide to Mailing.

This article is intended to cover some of the rules so you will not be surprised at the counter.

Rules at the Post Office

Know how to find the rules:

  1. The United States Postal Service has rules and regulations for mailing and shipping, and the guide for the domestic mail is called the DMM.

Realize there the rules are always changing:

  1. The DMM is updated from time to time.
    • There are also directives that come to the local post office, so just when you think you know the rules, they change them.
    • The fun ones are the little-known ones that they apply depending upon the clerk's mood that day.

Understand the letter regulations:

  1. A letter must be at least 5 inches long and 3 1/2 inches tall.
    • If you bring something the size of a postcard, they will likely refuse it unless it is a postcard.
  2. You cannot use origami for the envelope.
    • It must be rectangular with parallel sides — Don't try to mail a heart shaped letter.
    • You will have to put it in a large envelope, and they will recommend Priority Mail at $4.95 minimum charge.
  3. If your letter is more than 13 oz. it automatically goes into a Priority Mail class.

Non-machinable Mail

Know about non-machinable mail:

There is a class called non-machinable mail that is for items that might look to you like an envelope, but not to the postal service.

  1. If you place the address parallel to the shorter side of an envelope, it becomes non-machinable.
  2. If you send anything with clasps or strings for closure, or if it is lopsided, too rigid, is in any way not in the class of a letter, it may become non-machinable mail.

This mail has a surcharge beyond the weight or zone.

Learn the difference in flats and parcels:

  1. A flat must be flexible, and the DMM gives a test to see if it is flexible enough to be a flat, along with three color drawings and extensive details.

Parcels: Little Known Regulations


  1. may weigh up to 70 lbs.
  2. length and girth combined must be less than 108 inches (Parcel Post can be 130 inches)
  3. A parcel must be 6 inches long or more, at least 3 inches high, and 1/4 inch thick
  4. It must weigh at least 6 oz

Then there are irregular parcels and outside parcels, ones that cannot be processed without some special treatment:

  1. Parcels addressed to zone 1-4 and that weigh less than 20 lbs. and are larger than 84 inches are charged a 20-pound rate. Ouch!
  2. Liquids have to be marked liquid on the outside.
  3. If you want to send a First Class lumpy envelope under 13 oz. and use Delivery Confirmation, it must be at least 3/4 inch thick.
    • Otherwise you will need to send it priority mail to get Delivery Confirmation.

If you have a package that does not arrive and it is not insured, you can get your postage back by completing a form at the local post office for services not rendered.

The postal clerks have a banner at the top of their computer that tells them to recommend Express and Priority Mail first, and to give information on Parcel Post only if asked. This is why you seldom hear them mention Parcel Post.

Other Tips

Few cities have next day delivery even express mail by the USPS. If you want something shipped in a rush, do not go to the USPS. They are not in the fast delivery business.

Clerks have the option to accept or deny any package that they believe may not make it to the destination safely—so if you do not pack to their satisfaction, particularly if you want it insured, they can deny the package.

If you need supplies, the USPS is not economical, although it may be convenient.

The cost of the Ready Post boxes, tape, bubble wrap, and other postal supplies is beyond the reach of the common man. Go to your local office supply or even a drug store on the way to the post office for any supplies you may need.

If you sell on the internet and ship regularly, you need to be friends with all the clerks at the local post office. Be patient, accept their decisions and suggestions with grace, and hope you get another clerk the next time.

1-800-222-1811 will let your order Priority Boxes and supplies "free". Of course they aren't free—you pay the higher postage at the counter.