Address Change Service:  An automated process that provides change-of-address information to participating mailers who maintain computerized mailing lists.

Address Correction Service:  A system of ancillary service endorsements that allows mailers to obtain the addressee's new (forwarding) address or the reason for nondelivery.

Ancillery Service:  Forwarding, return,or address correction service included within a mail class.

Area Distribution Center (ADC):  A mail processing facility that receives and distributes mail destined for specifice Zip codes.

Aspect Ratio:  The dimension of a mail piece expressed as a ratio of length divided by height. An aspect ratio between 1.3 and 2.5, inclusive, is required for automation compatibility.

Automated Area Distribution Center (AADC):  An area distribution center (ADC) that uses multilane optical character readers (MLOCRS), barcode sorters (BCSs), and other equipment designed for processing automation-compatible mail.

Automation-Compatible Mail:  Mail that can be scanned and processed by automated mail processing equipment such as a barcode sorter.

Automation Discount:  This is a discount offered to mailers who apply a pre-barcode to pieces that meet requirements for automation.

Barcode:  This is a series of vertical bars and spaces that represent the zip code for the delivery address.

Bound Printed Matter (BPM):  A subclass of Package Services that consists of permanently bound sheets of which at least 90% are printed with advertising, promotional, directory, or editorial matter (or a combination of such matter).

Bulk Mail Center (BMC):  This is a highly mechanized mail facility for processing bulk mail.

Business Mail Entry Unit (BMEU):  The area of a postal facility where mailers present presorted and permit mail for acceptance.

Code Accuracy Support System (CASS):  This is a service offered to mailers, service bureaus, and software vendors that help improve the accuracy of physical addresses and their respective zip codes.

Collect On Delivery (COD):  A service for mailers who need to mail an article for which they have not received payment. The amount due the sender is collected from the addressee and the USPS returns the amount due to the sender.

Dead Mail:  Mail that is undeliverable as addressed and cannot be returned to the sender (usually because there is no return address on the piece).

Delivery Confirmation:  A service that provides the date and time of delivery or, if delivery was attempted but not successful, the date and time of the delivery attempt.

Delivery Point Barcode (DPBC):  A POSTNET barcode that consists of 62 bars with beginning and ending frame bars and 5 bars each for the nine digits of the Zip+4 code, the last 2 digits of the primary street address number (or post office box, etc.), and a correction digit. The DPBC allows automated sortation of letter mail to the carrier level in walk sequence.

Direct Mail:  Another name for advertising mail sent to targeted markets.  It can be any mail class, but it is usually Standard Mail.

Endorsement:  An authorized marking on a mailpiece that shows handling instructions, a service, or a request for an ancillary service.

Express Mail:  A mail class that expedites the delivery of mail pieces.

Extended Managed Mail Tray (EMM) (also called "2 Ft. Trays"):  Two foot trays that measure 21 3/4" long by 11 1/2" wide (inside bottom dimensions) by 6 1/8" high. Must be used for letter size mail that does not fit in regular MM trays.

First Class Mail:  A mail class that includes all matter wholly or partly in writing or typewriting, all actual and personal correspondence, all bills and statements of account, and all matter sealed or otherwise closed against inspection.

Flat:  The general term for flat-size mail, so called because the large mail is sorted without bending it so that the mail remains flat.

Indicia:  An imprinted designation on mail that denotes postage payment.  It is typically located at the top right corner of the address area where a first class stamp goes.

Insert:  A letter, card, or similar item placed inside another mailpiece.

Irregular Parcel:  A mail processing category for a parcel that does not meet the dimensions of a machinable parcel.

Machinable:  The ability of a mailpiece to be sorted by mail processing equipment.

Machinable Parcel:  A parcel that is of the correct size and weight to be safely sorted by mail processing machinery such as a parcel sorting machine.

Mailing:  A group of mailpieces with the same mail class and mail processing category that may be sorted together under the appropriate standards.

Mailing Agent:  A private third party that mails on behalf of someone else.

Media Mail:  A subclass of package services that consists of books, sheet music, printed educational material, film, videocassettes, cd-roms, and other computer readable media.

Metered Mail:  Any mail class, except periodicals, with postage printed by a USPS-approved postage meter.

National Change of Address (NCOA):  An address correction service that the USPS provides to mailers thru USPS licenses. If there is an ancillary done on a mailing database over a year old, the NCOA is a must to keep the mailer from having excessive returned mail.

Nonmachinable:  The incapacity of a mailpiece to be sorted on mail processing equipment because of size, shape, content, or address legibility. Such mail must be processed manually and could be subject to a surcharge.

Nonprofit Rate:  A preferred rate for a Periodicals publisher authorized to mail as a nonprofit organization.

Oversized Rate:  Parcel Post rate for pieces exceeding 108 inches but not more than 130 inches in combined length and girth.

Parcel Post:  A subclass of Package Services with rates based generally on weight and zone.

Periodical:  A class of mail consisting of magazines, newspapers, or other publications formed on printed sheets that are issued at least four times a year. They require having a legitimate list of subscribers and requesters.

Permit:  Any authorization required for specific types of preparation of postage payment.

Postage Statement:  Documentation provided by a mailer to the USPS that reports the volume of mail being presented and the postage payable or affixed, and certifies that the mail meets the applicable eligibility standards for the rate claimed.

Presort:  The process by which a mailer prepares mail so that it is sorted to the finest extent required by the standards for the rate claimed.

Priority Mail:  First-Class Mail that weighs more than 13 ounces and, at the mailer's option, any other mail matter weighing less than 13 ounces mailed at Priority Mail rates. Priority Mail provides expedited delivery. Any mailable matter may be sent as Priority Mail.

Registered Mail:  Provides the most secure service offered by the USPS. The sender receives a receipt at the time of mailing, and a delivery record is maintained by the USPS.

Rural Route:  A delivery route served by a rural carrier.

Single-Piece Rate:  A postage rate available for individual pieces of Express Mail, Priority Mail, First-Class Mail, and Package Services. It is not available for Periodicals except under the rate category of basic.

Standard Mail:  This is a class of mail that weights less than 16 ounces. It comprises the subclasses of Regular Standard Mail, Nonprofit Standard Mail, Enhanced Carrier Route Standard Mail, and Nonprofit Enhanced Carrier Route Standard Mail.

Tray:  A container used in postal facilities to hold letters and First Class Mail flats. It is used as a basic unit of mail quantity, for purposes of preparing mail to qualify for discounted postage rates.

Walk Sequence:  The order in which a carrier delivers mail for a route. This order is required for most carrier route presort mail.

Zone Improvement Plan (ZIP):  Established in 1963, the system of 5-digit codes that identifies the individual post office or metropolitan area delivery station associated with an address. Zip+4 is an enchance code consisting of the 5-digit Zip Code and four additional digits that identify a specific range of delivery addresses.