Door Slots & Wall Mailboxes Approved Door Slots. Some homes and apartments have a slot in the door for receiving mail instead of a mailbox. The standards for an approved door slot are: The opening must be at least 1 1/2″ x 7″. The bottom of the slot must be at least 30″ above floor. Horizontal slots must have a flap hinged at the top. May be used for U.S.P.S. Residential door mail delivery; Made of brass; Letter size mail slot overall dimensions are 8-3/4' W x 2-7/8' H; Rough opening dimensions are 6-7/8' W x 1-3/4' H; Include an 8' W x 2' H spring loaded flap; Include 2 pieces - flap for the front of a wall or solid door and inside trim for the rear.

• How To Dimension Slots
• Standard Key Slot Dimensions

Sizes for Letters

You probably have a picture in your mind of what a 'letter' is. Possibly you're using a standard No. 10 envelope for your letter, so that's easy to picture. However, if you decide to create a mailpiece with its own special envelope or if you are designing a piece that will be folded to letter-size, be sure to keep in mind the following size requirements for letters:

To be eligible for mailing at the price for letters, a piece must be:

• Rectangular
• At least 3-1/2 inches high x 5 inches long x 0.007 inch thick.
• No more than 6-1/8 inches high x 11-1/2 inches long x 1/4 inch thick.

First-Class Mail letters that have one or more nonmachinable characteristics will pay a nonmachinable surcharge. Customers can be unpleasantly surprised that they must pay extra postage when, for example, they mail a square greeting card. The Postal Service charges extra postage because mailpieces that are rigid, square, or unusually shaped, often jam postal equipment and are difficult to process. This costs the Postal Service time and money—and may also damage your mailpiece.

Many mailers fold sheets of paper to form letter-size pieces or newsletters. Folded pieces, or folded self-mailers, can save time and money because you're not paying for or stuffing envelopes. Folded self-mailers must be sealed or they will be subject to the nonmachinable surcharge. We recommend that you use wafer seals or tabs to close the open sides of folded mailpieces.

Here's some good advice on tabbing: Put the fold on the bottom (the side below the address) and secure the opening at the top with a piece of tape, a tab or a wafer seal.

There are special size requirements for mailing letters at automation prices. Contact your Business Mail Entry Unit for more information.

How To Dimension Slots

TIPS

• 0.007 inches? How do I measure that? As a guide, an index card is thick enough. If in doubt, contact a Mailpiece Design Analyst (MDA) near you. MDAs have tools for precisely measuring thickness and can tell you if your mailpiece is thick enough.
• What is high? What is long? Length is the side parallel to the address. Height is the side that is perpendicular to the length.

Standard Key Slot Dimensions

1. Sizes for parcels that weigh 13 ounces or less.