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USPS Postal Glossary

Additional Entry (AE)—A post office other than the office of original entry where a publisher is authorized to mail a Periodicals publication.

Address Change Service (ACS)—An automated process that provides change-of-address information to participating mailers who maintain computerized mailing lists. The information is captured in Computerized Forwarding System (CFS) units and sent to mailers on electronic media, which reduces the volume of manual change-of-address notices.

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.

Address Element Correction (AEC)—A process that identifies and revises incomplete or incorrect computerized address files and then attaches ZIP+4 and carrier route codes. It involves computer matching address records that cannot be coded using CASS-certified address matching software.

Airport Mail Center/Airport Mmail Facility (AMC/AMF)—A postal facility at an airport that receives, concentrates, transfers, dispatches, and distributes mail transported by air.

Alternate Mailing System (AMS)—A procedure, authorized by the manager, Business Mailer Support, that provides methods for accepting permit imprint mail to ensure proper postage payment and mail preparation without verification by weight.

All Purpose Container (APC)— a postal container for holding mail and parcels. These containers will need the Intelligent Mail container barcode in starting January 2009. DAT-MAIL™ currently supports the Intelligent Mail container barcode.

Ancillary Service—Forwarding, change, return, or address correction service included within a mail class. Depending on the mail class, these services are performed at a charge or at no additional charge, if and when the service is actually provided.

Ancillary Service Endorsement—A marking used by a mailer to request the new address of an addressee and to provide the USPS with instructions on how to handle mail that is undeliverable as addressed.

Area Distribution Center (ADC)—A mail processing facility that receives and distributes mail destined for specific ZIP Codes. ADCs and their associated ZIP Codes are in DMM labeling list.

Army Post Office (APO)—A branch of a designated USPS civilian post office, which falls under the jurisdiction of the postmaster of either New York City or San Francisco, that serves either Army or Air Force personnel. Window Book's Postal Package Partner™ shipping software has all the APO/MPO/FPO data updated regularly.

Aspect Ratio—The dimension of a mailpiece expressed as a ratio of length divided by height (for letters and cards, length is the dimension parallel to the address as read). For example, a postcard 5-1/2 inches long by 3-1/2 inches high has an aspect ratio of 1.57. An aspect ratio between 1.3 and 2.5, inclusive, is required for automation compatibility.

Automated Area Distribution Center (AADC)—A distribution center that uses multiline optical character readers (MLOCRs), barcode sorters, 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—A postage reduction offered to mailers who barcode their mailpieces and meet addressing, readability, and other requirements for processing on automated equipment.

Auxiliary Service Facility (ASF)—A mail processing facility that has its own service area and serves as a satellite processing hub for a particular bulk mail center (BMC)

Balloon Rate—A rate charged for Priority Mail (zones 1-4) and Parcel Post items that weigh less than 20 pounds and measure between 84 and 108 inches in combined length and girth.

Barcode—A series of vertical bars and spaces that represent any numerical series, most often a correct ZIP Code for the delivery address on a mailpiece. The barcode facilitates automated processing by barcode readers and scanners. A barcode also can be used to convey information for Delivery Confirmation and Signature Confirmation services. Barcodes that may be used for postal processing are POSTNET, Intelligent Mail, and UCC/EAN Code 128.

Barcode Clear Zone—A rectangular area in the lower right part of a letter-size mailpiece that must be kept free of printing and symbols, except for the barcode itself. This requirement allows automated processing machines to read or apply a barcode.

Barcode Read Area—A small area within the barcode clear zone in which the barcode must be printed. This area is defined by the position of the leftmost bar of the barcode and the bottom edge of the bar.

Barcode Scanner—A barcode reader with integrated scanning component that interprets the barcode applied to a mailpiece. Window Book carries Metrologic Scanners

Barcoded Container Label—A tray or sack label that has a barcode that can be read and processed by an automated tray or sack handling system.

Barcoded Discount—A postage discount available for certain Package Services machinable parcels and Bound Printed Matter flats that bear a correct barcode and meet other size, shape, and volume requirements.

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—Mail that is rated for postage partly by weight and partly by the number of pieces in the mailing. The term is generally used to refer to Presorted First-Class Mail and Standard Mail.

Bulk Mail Center (BMC)—A highly mechanized mail processing plant that distributes Standard Mail and Package Services in piece and bulk form. These have been renamed to Network Distribution Center (NDC).

Bulk Mail Center (BMC) Presort Rate—A rate available for Parcel Post that is properly prepared and entered by the mailer at a BMC or other designated postal facility.

Bulk Parcel Return Service (BPRS)—A service by which high-volume mailers may have undeliverable-as-addressed Standard Mail machinable parcels returned to the mailer.

Bundle—A group of addressed pieces assembled and secured together to make up a basic unit of bulk mail for processing purposes.

Business Mail Entry Unit (BMEU)—The area of a postal facility where mailers present bulk, presorted, and permit imprint mail for acceptance. The BMEU includes dedicated platform space, office space, and a staging area on the workroom floor.

Business Reply Mail (BRM)—A service that allows a permit holder to receive First-Class Mail and Priority Mail back from customers and pay postage only for the returned pieces. These pieces must have a specific address and format. Postage and per piece charges are collected when the mail is delivered back to the permit holder.

Caller Service—An optional delivery service provided for a fee at all post offices to customers with large volumes of mail, to customers needing multiple separations, and to customers who need a post office box number address when no post office boxes are available.

Carrier Route—The addresses to which a carrier delivers mail. In common usage, carrier route includes city routes, rural routes, highway contract routes, post office box sections, and general delivery units.

Carrier Route File—The official listing of all city and non-city delivery post offices, available to mailers in a standardized format. It contains schemes for city routes, rural routes, highway contract routes, post office box sections, and general delivery units. The data is formatted by ZIP Code, street name, and street number range.

Carrier Route Presort Mail—Mail sorted by carrier route to qualify for discount postage rates. The mail requires no primary or secondary distribution. The term is a general descriptor of the available rates for this type of preparation, which includes Enhanced Carrier Route Standard Mail, carrier route Periodicals, and carrier route Bound Printed Matter.

Centralized Postage Payment System (CPP)—A postage payment system that allows publishers of authorized Periodicals publications entered at three or more post offices to pay postage at a single postal facility rather than through individual accounts maintained at each entry post office.

Certified Mail—A service that provides the sender with a mailing receipt. A delivery record is maintained by the USPS. This type of mail must be sent at First-Class Mail or Priority Mail rates. Certified mail may be combined with return receipt service and restricted delivery service.

Classification—The grouping of mailable matter into mail classes and subclasses by rate categories, according to content, weight, size, and preparation standards.

Classroom rate—A Periodicals rate that is available to an authorized mailer of educational, scientific, or religious publications for scholastic or religious instruction.

Coding Accuracy Support System (CASS)—A service offered to mailers, service bureaus, and software vendors that improves the accuracy of matching to delivery point codes, ZIP+4 codes, 5-digit ZIP Codes, and carrier route codes on mailpieces. CASS provides a common platform to measure the quality of address matching software and to diagnose and correct software problems. An Overview of the CASS Program and list of CASS certified vendors are available on

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.

Combined Mailing—A mailing in which individually addressed mailpieces are merged and sorted together, usually using two or more postage payment methods.

Commercial Mail Receiving Agency (CMRA)—A private business that acts as the mail receiving agent for specific clients by providing a delivery address and other services.

Commingle—To integrate dissimilar mail (such as subscriber and nonsubscriber copies or machinable and irregular parcels) into the same mailing.

Computer-readable Media—A DVD, CD (compact disk), and CD-ROM are mailable at single-piece and discount rates based on the packaging or mailer and contents. For more information, contact your Business Mail Entry office.

Computerized Forwarding System (CFS)—A centralized, computerized address label-generating operation that performs address correction and forwards or returns undeliverable-as-addressed mail to customers.

Content Identifier Number (CIN)—A code number on a tray or sack label that represents and identifies the class of mail and presort level.

Cooperative Mailing—A mailing made jointly by one or more organizations authorized to mail at Nonprofit Standard Mail rates at the same post office.

Copalletize—To combine and present together on pallets mail from two or more different or separately produced mailstreams. Also, refer to DAT-MAIL™'s Palletization Module.

Courtesy Pallet—Un-palletized trays or sacks. DAT-MAIL™ Toolbox includes a Palletization Utility for building courtesy pallets.

Courtesy Reply Mail (CRM)—Envelopes or postcards that a mailer provides to its customers to expedite delivery of their responses. The customer affixes the reply postage before mailing.

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. This service may be obtained in two forms: (1) an electronic option for mailers who apply identifying barcodes to each piece, provide an electronic file, and retrieve delivery status information electronically; and (2) a retail option for mailers who retrieve delivery status through the USPS Internet at or by calling 800-222-1811.

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 in carrier walk sequence.

Delivery Sequenced Mail—Mail that is arranged by a mailer in delivery order for a particular carrier route. This mail requires no primary or secondary distribution.

Destination Area Distribution Center (DADC) Rate—A rate available for Periodicals mail that is prepared and entered by the mailer at the area distribution center (ADC) that serves the delivery address on the mail.

Destination Bulk Mail Center (DBMC) Rate—A rate available for Standard Mail, Parcel Post, and Bound Printed Matter that is properly prepared and entered by the mailer at the BMC or other designated postal facility that serves the delivery address on the mail.

Destination Delivery Unit (DDU) Rate—A rate available for Periodicals, Standard Mail, Parcel Post, and Bound Printed Matter that is properly prepared and entered by the mailer at the delivery unit that serves the delivery address on the mail.

Destination Sectional Center Facility (DSCF) Rate—A rate available for Periodicals, Standard Mail, Parcel Post, and Bound Printed Matter that is properly prepared and entered by the mailer at the sectional center facility (SCF) or other designated postal facility that serves the delivery address on the mail.

Detached Address Label (DAL)—Paper or cardstock used to carry address information when preparing a mailing of unaddressed Periodicals flats, Standard Mail flats and merchandise samples, and Bound Printed Matter.

Detached Mail Unit (DMU)—An area in a mailer's facility where postal employees perform mail verification, acceptance, dispatch, and other postal functions.

Dimensional Weight—Postage for Priority Mail packages addressed for delivery to zones 5-8 and exceeding one cubic foot (1,728 cubic inches) is based on the actual weight or the dimensional weight, whichever is greater. Dimensional weight is sometimes referred to as dim weight.

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

Dimensional Weight—Postage for Priority Mail packages addressed for delivery to zones 5-8 and exceeding one cubic foot (1,728 cubic inches) is based on the actual weight or the dimensional weight, whichever is greater.

Drop Shipment—Typically the movement of a mailer's product on private (nonpostal) transportation from the point of production to a postal facility located closer to the destination of that product. DAT-MAIL™ Toolbox includes a DropShipIT module for processing drop shipping.

eDoc—Electronic Documentation

Eligibility—Qualification standards such as content, mail processing category, and preparation applied to mail for a specific rate or discount.

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

Enhanced Carrier Route Standard Mail—Two subclasses of Standard Mail (Regular and Nonprofit).

Entry BMC—A bulk mail center (BMC), including its satellite auxiliary service facility (ASF) unless specified otherwise, at which mail is entered by the mailer. Also see Bulk Mail Center (BMC) and Auxiliary Service Facility (ASF).

Entry Facility—The USPS mail processing facility (e.g., BMC, SCF) that serves the post office at which the mail is entered by the mailer. Also called origin facility.

Entry Post Office—A post office at which a mailer deposits mailings to be paid for through an account maintained at the designated post office.

Express Mail—A mail class that provides expedited delivery service. This is the fastest mail service offered by the USPS. Express Mail International Service is available between the United States and most other countries.

Express Mail Military Service (EMMS)—An Express Mail service available between the United States and designated APO and FPO addresses that provides Department of Defense and other authorized personnel stationed overseas with expedited delivery service to or from the United States.

Extended Managed Mail Tray (EMM)—A 2-foot letter tray that measures 21-3/4 inches long by 11-1/2 inches wide (inside bottom dimensions) by 6-1/8 inches high. Must be used for "tall" letter-size mail that does not fit in a regular managed mail (MM) tray.

Face—The side of a mailpiece with the delivery address. Also, to arrange mail in a uniform orientation; that is, with the delivery address facing forward and the postage area positioned in the upper right corner.

Facing Identification Mark (FIM)—A series of five or six vertical bars used by automated postal equipment to identify, orient, and separate reply mail and mail produced by PC postage systems and some postage meters.

Facing Slip—A paper label attached to the top of a bundle that shows where the mail is to be distributed, the class and type of mail, and the country or military post office. Also see optional endorsement line.

Fast Access and Shipment Tracking System (FAST)—FAST is designed to make drop shipping with USPS more efficient, saving mailers time through electronic notification of mailing, automatic tracking of appointments, and a revamped system for making drop ship appointments. DAT-MAIL™ supports FAST and PostalOne!
Refer to FAST/Surface Visibility link at FAST uses USPS PostalOne! portal, and you must register there to access the program: Customer Care Center: 800-522-9085.

FASTforward—A USPS-licensed automated system that updates addresses by matching names and addresses with current change-of-address orders on file. A piece updated with FASTforward can be delivered directly to the new address rather than forwarded from the old address.

Federal Register—A daily weekday publication distributed by the Office of the Federal Register in which certain U.S. government documents must be published. The USPS publishes proposed and final mail preparation changes in the Federal Register for public comment and notice. A listing of Postal Service Federal Register Notices is available at

First-Class Mail (FCM)—A class of mail 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. Priority Mail is a subclass of First-Class Mail. Any mailable matter may be sent as First-Class Mail.

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.

Flat-size Mail—A flexible rectangular mailpiece that exceeds one of the dimensions for letter-size mail (11-1/2 inches long, 6-1/8 inches high, 1/4 inch thick) but that does not exceed the maximum dimension for the mail processing category (15 inches long, 12 inches high, 3/4 inch thick). Dimensions are different for Periodicals automation rate flat-size mail. Flat-size mail may be unwrapped, sleeved, wrapped, or enveloped.

Fleet Post Office (FPO)—A branch of a designated USPS civilian post office, which falls under the jurisdiction of the postmaster of either New York City or San Francisco, that serves Coast Guard, Navy, or Marine Corps personnel. Also see military post office. Window Book's Postal Package Partner™ shipping software has all the APO/MPO/FPO data updated regularly.

FLTS—An abbreviation used on mail container labels that identify the contents as flat-size.

Forward—To redirect mail to the intended recipient's new delivery address in cases where PS Form 3575, Change of Address Order, or other written or personal notice has been filed with the local post office. Also see Address Change Service (ACS), Address Correction Service.

Franked Mail—Official mail sent without postage prepayment by members and members-elect of Congress, the Vice President, and other authorized individuals. Mail must relate to the mailer's official business, activities, and duties. The mailpiece bears a written signature, printed facsimile signature, or other required marking instead of a postage stamp.

Full Flat Tray—A tray that is sufficiently filled with flats to allow or require preparation to the corresponding presort destination. A full flat tray contains at least enough pieces so that a single stack of mail lying flat on the bottom of the tray reaches to the bottom of the handholds. Additional pieces must be added when possible to physically fill the tray.

Full Letter Tray—A full tray is filled between 85% and 100% with faced, upright pieces. Each tray must be physically filled to capacity before the filling of the next tray.

Full Sack—A sack filled with the minimum number of pieces needed to qualify for the class and rate claimed.

Gateway — An important transportation center, especially for air transportation, where mail routes converge and mail is rerouted for onward dispatch. (Also called consolidation point.)

General Delivery — An alternate delivery service that allows customers with proper identification to pick up mail at post offices. Provided primarily at offices without letter carrier delivery or for transients and customers who do not have a permanent address or who prefer not to use post office boxes. (Also see poste restante.) (Compare with caller service.)

General Mail System (GMS) — The entire postal system, including the bulk mail network and all postal field operations. (Compare with National Bulk Mail System.)

General Post Office (GPO) — (obsolete) (See main post office.)

General Purpose Mail Container (GPMC) — A wheeled container that is nestable (that is, it can be stored in an L-shaped configuration) and is used to transport, stage, and distribute sacks, trays, and bundles. More than 5 feet tall, with a capacity of 1,200 pounds of mail, the container can be pushed by hand or pulled by tractor. (Compare with eastern region mail container.)

General Scheme — A pattern of distribution of mail for a state or section of a state that shows the route or supply by which each post office receives mail.

Girth — The measurement around the thickest part of a mailpiece.

Global ePOST — An electronic-to-hard copy service that provides mailers with one-stop shopping for international mailings. Designed for large-volume mailers needing a fast, secure, and reliable way to send international mail, such as invoices, orders, account statements, and advertisements.

Global Package Link — An air export service that provides end-to-end solutions (e.g., varying service levels, customs clearance, tracking) for international volume package shipping.

Global Priority Mail (GPM) — An expedited international service for the shipment of documents, correspondence, and merchandise, featuring a 4-business-day delivery standard to selected countries in Europe, the Pacific Rim, and Canada.

Gondola — (informal) A six-wheeled container or tub used to move pouches, sacks, and nonsackable mail. (Also see basket.)

Governors — (See Board of Governors.) gravity roller conveyor — (See conveyor.)

Gross Combined Weight (GCW) — The combined total vehicle weight of a tractor and trailer.

Gurney — (See basket.)

Hazardous Material (HAZMAT)—Any article or substance designated by the U.S. Department of Transportation (DOT) as being capable of posing an unreasonable risk to health, safety, and property during transportation.

Highway contract route (HCR)—A route of travel served by a postal contractor to carry mail over highways between designated points. Some HCRs include mail delivery to addresses along the line of travel. Formerly called star route.

Identical Piece—An individual mailpiece that has the same mail classification and physical aspect, size, and weight as all other pieces in a mailing.

Indicia—Imprinted designation on mail that denotes postage payment (e.g., metered postage or permit imprint).

Information-based Indicia (IBI)—Digital indicia that include human-readable information and a USPS-approved two-dimensional barcode with a digital signature and other required fields.

Insert—A letter, card, or similar item placed inside another mailpiece (host piece).

Insured Mail—A service that provides indemnity coverage for a lost, rifled, or damaged article, subject to the standards for the service and payment of the applicable fee. Insurance is available for merchandise sent as First-Class Mail, Express Mail, Priority Mail, Standard Mail, and Package Services.

Intelligent Mail Barcodes—The new barcodes are designed to sort and track mailpieces faster and more efficiently. It will provide greater visibility and faster USPS acceptance and verification.

Intelligent Mail Container Barcode—Barcode applied to a placard with unique mail preparer ID, and unique pallet, container, APC, rolling stock.

International Mail Manual (IMM)—The USPS manual that contains rates and classification standards for mailing between the United States and Canada, Mexico, England, France, Germany, China, Japan, Australia, and all other countries.

International Standard Book Number (ISBN)—A publication number issued by the Library of Congress that identifies a specific book or other nonperiodical.

International Standard Serial Number (ISSN)—A publication number issued by the Library of Congress that identifies a specific periodical (such as a Periodicals publication).

Keyline—Optional mailer information printed in or above the address or in the lower left corner of the envelope. The information in a keyline identifies the mailpiece and its presort level. Under some postage payment systems, the keyline is a required line that contains specific information about the mailpiece.

Known Office of Publication—The business office of a Periodicals publication that is in the city where the original entry for Periodicals mailing privileges is authorized.

Less-than-full Tray—A tray that contains mail for a single destination that was not preceded by a full tray for that destination. Less-than-full trays may be prepared only if permitted by the standards for the rate claimed.

Letter—According to the Private Express Statutes, a message directed to a specific person or an address and recorded in or on a tangible object. Also a shortened way to refer to letter-size mail.

Letter-size Mail—A mail processing category of mailpieces, including cards that do not exceed any of the dimensions for letter-size mail (i.e., 11-1/2 inches long, 6-1/8 inches high, 1/4 inch thick).

Library Mail—A subclass of Package Services for items sent to or from or exchanged between academic institutions, public libraries, museums, and other authorized organizations. Books, sound recordings, academic theses, and certain other items may be mailed at the Library Mail rate if properly marked.

line-of-travel (LOT) sequence—A sequence required for some Enhanced Carrier Route and carrier route rates in which mailpieces are arranged by ZIP+4 codes in the order in which the route is served by the carrier. The mailpieces are sequenced in delivery order.

LTR (or LTRS)—An abbreviation used on mail tray labels that identifies the contents as letter-size pieces.

MACH—An abbreviation used on mail container labels that identifies the contents as machinable letters or parcels (mail that can be processed on mechanized mail sorting equipment).

Machinable—The ability of a mailpiece to be sorted by mail processing equipment. Compare with nonmachinable.

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.

Mail—Any mailable matter that is accepted for mail processing and delivery by the USPS. Also, the sum total of the mail at any time that is in USPS custody. To deposit a mailable item in a collection box or present the item (or a mailing for large quantities of mailpieces) at a post office or business mail entry unit.

Mail.dat—The industry standard database file set, consisting of detailed presort mailing info. It is created during the presort process by a presort software or MLOCR machine and consists of data element in a readily usable format that is the only electronic mailing info accepted by USPS. DAT-MAIL™ imports and validates Mail.dat files AND creates statements for non-Mail.dat mailings.

Mail Class—The classification of domestic mail according to content (e.g., personal correspondence versus printed advertising). It is codified in the Domestic Mail Classification Schedule.

Mailers' Technical Advisory Committee (MTAC) —MTAC provides a venue for exchange of technical info and recommendations regarding mail related services and issues. It is composed of major mailing associations that work collaboratively with the Postal Service to benefit the mailing industry. Window Book's clients are represented at MTAC via Window Book's postal specialists who participate in MTAC.

Mailer ID (MID)—6 or 9 digit Mailer identifier assigned by USPS.

Mailer ID Assignment Helpdesk info:
PostalOne!: 800-522-9085 for Letter & Flat mailers, and Intelligent Mail barcodes on trays, sacks, tubs and containers.
Confirmation Service: 877-264-9693 for Package Mailers
Confirm: 800-238-3150 to use OneCode Confirm
ACS: 800-238-3150 to use OneCode ACS

Mailpiece Quality Control Program (MQC)—The Mailpiece Quality Control Program is designed for those who wish to enhance their knowledge of the requirements associated with mailpiece design. It is a self-paced, self-study training program available on Postal Explorer.

Mailing—A group of mailpieces within the same mail class and mail processing category that may be sorted together under the appropriate standards. Also, the action of depositing or presenting mail at a post office.

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

Mailing Standards of the United States Postal Service, Domestic Mail Manual (DMM)—The USPS manual that contains the standards governing domestic mail services, descriptions of the mail classes and services and conditions governing their uses, standards for rate eligibility and mail preparation, and all postage rates and fees. Domestic mail is classified by size, weight, shape, content, service, and other factors.

Managed Mail (MM) tray—A stackable cardboard or plastic container with an enclosing cardboard sleeve and plastic strap that is used to transport letter mail to or between post offices.

Manifest Mailing System (MMS)—An automated, computer-supported system that enables a mailer to document postage and fees for all pieces in a mailing paid via permit imprint. This postage payment system enables the USPS to accept and verify permit imprint mailings that contain non-identical-weight and/or non-identical-rate pieces. These pieces are prepared by the mailer according to certain standards and require specialized documentation. Refer to Window Book's Postal Package Partner™, shipping and manifesting software, which will make your shipping with the U.S. Postal Service simple and inexpensive.

Marking—Words or abbreviations printed on a mailpiece that show the class of mail, presort level, or ancillary service endorsement. See also endorsement.

Media Mail—A subclass of Package Services that consists of books, sheet music, printed educational material, film, videocassettes, and computer prerecorded media such as CD-ROMs. Advertising restrictions apply.

Merchandise return service—A service whereby an authorized company provides a customer with a special mailing label to return a shipment without prepaying postage. The company pays the return postage.

Merlin—An acronym for Mail Evaluation Readability Lookup Instrument. It is a tool that is used by the U.S. Postal Service to assist with the acceptance of business mail.

Meter Reply Mail (MRM)—A preprinted return envelope, card, or label provided by a meter license holder as a courtesy to customers on which the postage is prepaid with a meter stamp. These pieces must have a specific address and format. Compare to business reply mail and courtesy reply mail.

Meter Stamp—Postage printed on a mailpiece or label by a postage meter or PC Postage System. Meter stamps may be used to pay postage for all mail classes except Periodicals.

Metered Mail—Any piece of mail with postage printed by a USPS-approved postage meter or PC Postage System.

Military Ordinary Mail (MOM)—A category for Department of Defense official mail sent at Periodicals or Standard Mail rates that requires faster service than sealift transportation to, from, and between military post offices. This mail is moved by surface transportation to a gateway facility and from there by air at a specific transportation rate and service standard.

Military Post Office (MPO)—A branch of a U.S. civil post office operated by the Army, Navy, Air Force, or Marine Corps to serve military personnel overseas or aboard ships. Refer to Window Book's Postal Package Partner™, a shipping software which updates APO/MPO/FPO data regularly.

Minimum Size Standard—The smallest dimensions permitted for all mailable matter or for a specific mail processing category or specific rate.

Mixed Class—A mailing containing more than one class of mail. With certain exceptions, the postage on the entire piece or bundle is charged at the rate of the higher class.

MXD—An abbreviation used on mail container labels that identifies the contents as mixed mail for different destinations. Usually indicates the last presort level in a sequence.

National Change of Address Linkage System (NCOALink)—An address correction service that the USPS provides to mailers through USPS licensees. The licensees match mailing lists submitted to them on tape or disk against change-of-address information for the entire country from all Computerized Forwarding System units. If a match is made, NCOALink can correct the address before it is printed on a mailpiece.

Network Distribution Center (NDC) — The new name for what was a BMC. Highly mechanized mail processing plants that are part of the USPS network distribution system.  These facilities distribute Standard Mail, Periodicals Mail, and Package Services Mail in bulk volumes.

Nonmachinable—The inability of a mailpiece to be sorted on mail processing equipment because of size, shape, content, or address legibility. Such mail must be processed manually.

Nonmachinable Outside (NMO)—A parcel or mailpiece that, because of size, weight, or other characteristic, cannot be sorted by mechanized mail processing equipment and must be handled manually. The parcel is called an outside because it cannot be placed in a sack or other mailing container.

Nonmailable Articles and Substances—Anything that, by statute, "may kill or injure another, or injure the mails or other property." There are some exceptions to this rule that allow otherwise unmailable items to be mailed.

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

Nonprofit Standard Mail—A subclass of Standard Mail that is available only to qualified organizations specified by U.S. statute.

Nonprofit Standard Mail EligibilityPublication 417, Nonprofit Standard Mail Eligibilitydiscusses eligibility, authorization, and the rules for mailing at the Nonprofit Standard Mail rates. Many customers find it helpful to reference this publication to gain authorization and determine the eligibility of their mailpiece.

Not Flat-Machinable Pieces—a subclass of Standard Mail also known as "NFMs." Most NFMs are rigid parcel-like pieces that cannot be processed on flat sorting equipment.

Official Mail—Mail authorized by federal law to be sent by government officials without postage prepayment. It includes franked mail sent by members of Congress and penalty mail sent by U.S. government agencies.

Optical Character Reader (OCR)—An automated mail sorting machine that interprets the address information on a letter-size mailpiece and sprays the corresponding ZIP Code information onto the piece as a barcode.

Optional Endorsement Line (OEL)—A series of specific printed characters on the top line of the address block that identifies the sortation level of a bundle and may contain an ACS participant code. The OEL is used in place of bundle labels.

Origin Bulk Mail Center (OBMC) Presort Rate—A rate available for Parcel Post that is properly prepared and entered by the mailer at the origin BMC or other designated postal facility.

Overflow Tray—A less-than-full tray that contains pieces remaining after preparation of full trays for the same destination. Overflow trays may be prepared only if allowed by the standards for the rate claimed.

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

Package Services—A class of mail that comprises four subclasses: Bound Printed Matter, Library Mail, Parcel Post, and Media Mail. There is no minimum weight limit for Package Services.

Pallet—A reusable platform on which mail is stacked to be moved as a single unit. Pallets are made of rigid material designed for four-way forklift entry and capable of handling loads of up to 65 cubic feet and 2,200 pounds. A USPS pallet measures 48 by 40 inches. Refer to DAT-MAIL™'s Palletization module for creating pallet placards and barcoded skid sheets.

Parcel—Mail that does not meet the mail processing category of letter-size mail or flat-size mail. It is usually enclosed in a mailing container such as a box.

Parcel Airlift (PAL)—A service that provides air transportation for parcels on a space-available basis to or from military post offices outside the 48 contiguous states.

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

PC Postage System—A postage system used to purchase and print postage with a personal computer, a printer, and Internet access.

PS Form 8017—Expedited Plant-Load Shipment Clearance.  Provides proof to the United States Postal Service (USPS) that a shipment of mail was verified and paid for at the origin-entry post office.

Penalty Mail—Official mail sent without postage prepayment by officers of the executive and judicial branches of the U.S. Government, by departments and agencies of the U.S. Government, and by specifically authorized individuals. Agencies then reimburse the USPS for the penalty mail service they receive. The term comes from the endorsement "Penalty for Private Use" printed on the mail. Compare to franked mail.

Periodicals—A class of mail consisting of magazines, newspapers, or other publications formed of printed sheets that are issued at least four times a year at regular, specified intervals (frequency) from a known office of publication. Periodicals usually must have a legitimate list of subscribers and requesters.

Permit—Any authorization required for specific types of preparation or postage payment. Specifically, an authorization to mail without postage affixed by using indicia or an imprint. Payment is made against an advance deposit account that is established with the USPS for postage and services. Permits also are required to participate in certain programs such as business reply mail.

Permit Imprint—Printed indicia, instead of an adhesive postage stamp or meter stamp, that shows postage prepayment by an authorized mailer.

Piece Rate—For some mail classes, the postage charged for each mailpiece in addition to the pound rate charge.

Plant-verified Drop Shipment (PVDS)—A procedure that enables origin verification and postage payment for shipments transported by the mailer from the mailer's plant to destination post offices for USPS acceptance as mail. PVDS is typically used for mailings for which a destination entry discount is claimed.

Post-presort software—Unlike presort software which focuses on addresses, post-presort software focuses on mailing. It utilizes presort Mail.dat output and generates mailing statements. DAT-MAIL™ is a complete mailing management software that generates postal statements and comprehensive accounting reports. Post-presort software like DAT-MAIL™ gives you the flexibility to adapt to last minute changes and requirements with easy and accuracy.

Postage—Payment for delivery service that is affixed or imprinted to a mailpiece, usually in the form of a postage stamp, permit imprint, or meter stamp.

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.

Postal Customer Council Program—A national program that provides mailers with a forum for exchanging ideas for improved mail service and discussing new and existing USPS products, programs, regulations, and procedures.

Postal Numeric Encoding Technique (POSTNET)—The barcode system used on letter-size and flat-size mailpieces for encoding the delivery point information and ZIP+4 code information.

PostalOne!—Electronic service that links your mailing info electronically with Postal Service for acceptance, verify payment systems, and eliminate most of the paperwork.
To register for PostalOne! portal: go to .
Customer Care Center: 800-522-9085,
Window Book's mailing software, DAT-MAIL™, supports USPS PostalOne! and FAST drop ship appointments.

Postcard—A privately printed mailing card.

Precancel—To cancel postage stamps or stamped envelopes before mailing. If authorized, bulk mailers may precancel their own postage.

Precanceled Stamp—A postage stamp canceled by marking across the face before it is sold to mailers for use with discount mailings. Also, a stamp designated by the USPS as a precanceled stamp without cancellation marks. The USPS sells precanceled stamps for Presorted First-Class Mail and regular and nonprofit Standard Mail. Mailpieces with these stamps do not go through a canceling machine at the time of mail processing.

Presort—The process by which a mailer groups mail by ZIP Code so that it is sorted to the finest extent required by the standards for the rate claimed. Generally, presort is performed sequentially, from the lowest (finest) level to the highest level, to those destinations specified by standard and is completed at each level before the next level is prepared. Not all presort levels are applicable to all mailings.

Also, refer to DAT-MAIL™, a post-presort software that lets you go beyond presort by giving you the flexibility to adapt to last minute changes easily.

Presort Accuracy Validation and Evaluation (PAVE)—A program that evaluates presort software and determine its accuracy in sorting address files under DMM standards. An overview of the program and a list of PAVE Certified vendors are available on

Presorted Standard—The postage rate for Standard Mail pieces that are part of a mailing and that meet minimum volume and preparation requirements.

Pricing and Classification Service Center (PCSC)—A USPS field office that provides guidance to employees and customers on mail classification, postage rates, and mail preparation.

Printed Matter—Paper on which words, letters, characters, figures, or images (or any combination of them) not having the character of a bill or statement of account, or of actual and personal correspondence, have been reproduced by any process other than handwriting or typewriting.

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.

Processing and Distribution Center/Facility (P&DC/F)—A central mail facility that processes and dispatches part or all of both incoming mail and outgoing mail for a designated service area. It also provides instructions on the preparation of collection mail, dispatch schedules, and sorting plan requirements to mailers. The facility is usually a sectional center facility or a general mail facility, but it can also be a dedicated mail processing facility without a post office station or branch.

Prohibited Matter—Any material that is illegal to mail because it can kill or injure an individual or damage other mail. This includes certain poisons and controlled substances and certain flammable or hazardous matter.

Qualified Business Reply Mail (QBRM)—Business reply mail that is processed and rated by automated means, including the automated calculation of postage and fees. QBRM pieces must meet certain design specifications and may be eligible for the lowest per piece fee available for BRM and for reduced automation First-Class Mail postage rates. See QSG 507a.

Quick Service Guide—Publication 95, Quick Service Guide contains most of the Quick Service Guides available on Postal Explorer. Pub 95 is not available online.

Raffle Tickets—For an overview of the eligibility of lottery advertisements by authorized nonprofit organizations, see Customer Support Ruling 307.

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. This service also provides optional indemnity in case of loss or damage. Compare with certified mail and insured mail.

Restricted Delivery—A supplemental mail service that generally limits who may receive an item. This service is available for a fee when used with Certified Mail, collect on delivery, insured mail, and Registered Mail.

Restricted Matter—Any item on which certain mailing restrictions have been imposed for legal reasons other than risk of harm to persons or property involved in moving the mail and that require specific endorsements and markings. Examples include odd-shaped items in envelopes, motor vehicle master keys, and locksmithing devices as well as odor-producing materials, certain liquids and powders, and battery-powered devices. Compare to hazardous material.

Rural Route (RR)—A delivery route served by a rural carrier.

Scheme—Systematic plan for the distribution of mail to its destination.

Scheme Sort—The distribution of mail to its destination according to a systematic plan determined by the mail processing functional area. Typically, a scheme sort allows mailers to combine pieces addressed to two or more 5-digit or 3-digit ZIP Code areas.

Science-of-Agriculture rate—A Periodicals rate that is available to an authorized mailer of agriculture publications.

Sectional Center Facility (SCF)—A postal facility that serves as the processing and distribution center (P&DC) for post offices in a designated geographic area as defined by the first three digits of the ZIP Codes of those offices. Some SCFs serve more than one 3-digit ZIP Code range.

Seamless Acceptance—The Postal Service's strategy to radically streamline all processes related to business mail acceptance, documentation, scheduling, payment, and entry. The goal is to move to a complete electronic system that enables customers to transact all of the business of entering mail without having to submit paper documentation.

Shipper Paid Forwarding (SPF)—An address change service (ACS) fulfillment vehicle. It allows mailers of Standard Mail machinable parcels and most Package Services pieces to pay forwarding charges via approved ACS participant code(s).

Shortpaid Mail—Mail on which additional postage is collectable on final delivery.

Signature Confirmation—A service that provides information to the mailer about the date and time of delivery, including the recipient's signature or the date and time of the delivery attempt. This service may be obtained in two forms: (1) an electronic option for mailers who apply identifying barcodes to each piece, provide an electronic file, and retrieve delivery status information electronically; and (2) a retail option for mailers who retrieve delivery status through the Internet at or by calling 800-222-1811.

Single-piece Rate—A postage rate available for individual pieces of Express Mail, Priority Mail, First-Class Mail, Parcel Post, Media Mail, and Library Mail. It is not available for Periodicals except under the rate category of basic. This type of rate contrasts with rates available for discount mail.

Skew—The misalignment or slant of a character, bar, line of characters, or barcode with respect to the bottom or top edge of the mailpiece.

Sleeve—A paperboard jacket that fits over the four sides (top, bottom, and two parallel sides) of a letter tray in order to keep the mail inside the tray from falling out.

Stamped Card—A postcard sold by the USPS (as distinguished from a privately printed postcard) with a printed or impressed postage stamp. Compare to postcard.

Standard Mail—A class of mail that weighs 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. These subclasses include circulars, printed matter, pamphlets, catalogs, newsletters, direct mail, and merchandise. Standard Mail may be sent at Enhanced Carrier Route, automation, nonautomation, and Not Flat-Machinable rates.

Subclass—A subdivision of a mail class, usually based on the consideration of a physical characteristic rather than content.

Surcharge—An additional fee for nonstandard size mail or certain nonmachinable parcels.

Surface Transfer Center (STC)—Internal USPS facility that is used to facilitate transportation of mail across the country.  There are about 20 of these facilities located throughout the country.  These STCs are in the process of being integrated into the new Network Distribution Center (NDC) network.

Tag—A piece of cardboard or plastic that is attached to a pouch, sack or tray. It is usually in addition to the container label and is printed in various colors and provides info on contents, mail class and sortation type, routing instructions, and specific handling info. See DAT-MAIL for printing customizable sack and tray tags.

Tap Test—When a insert showing through the window is moved to any of its limits inside the envelope, the entire barcode must remain within the barcode clear zone, and a clear space must be maintained that is at least 1/8 inch between the barcode and the left and right edges of the window, at least 1/25 inch between the barcode and the top edge of the window, and at least 3/16 inch between the barcode and the bottom edge of the mailpiece.

Top Cap—Material that forms a flat, level surface horizontal to the base of a pallet that is used to protect the integrity of the mail under the top cap while also supporting a loaded pallet above. A top cap must be secured to a pallet of mail with either stretchwrap or at least two crossed straps or bands.

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.

Undeliverable-as-addressed (UAA)—Mail that the USPS cannot deliver as addressed and must forward to the addressee, return to the sender, or send to a mail recovery center.

Unique ZIP Code—A ZIP Code assigned to a company, government agency, or entity with sufficient mail volume, based on average daily volume of letter-size mail received, availability of ZIP Code numbers in the postal area, and USPS cost-benefit analyses.

United States Code (USC)—The official restatement of the general and permanent laws of the United States; 39 USC contains laws relating to the USPS.

Verification—The procedural checks of a mailing presented by a mailer to determine proper preparation and postage payment.

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

WKG—An abbreviation for "working" used on mail container labels that identifies the contents as mail that needs to be worked (sorted and distributed).

ZIP Code—a system of 5-digit codes that identifies the individual post office or metropolitan area delivery station associated with an address. ZIP+4 is an enhanced code consisting of the 5-digit ZIP Code and four additional digits that identify a specific range of delivery addresses. ZIP originally was an acronym for Zone Improvement Plan. The distance between two ZIP codes is as a number from 1 to 8 plus 0 (local).

ZIP+4 code—A nine-digit numeric code composed of two parts: (a) the initial code: the first five digits that identify the sectional center facility and delivery area associated with the address, followed by a hyphen; and (b) the four-digit expanded code: the first two additional digits designate the sector (a geographic area) and the last two digits designate the segment (a building, floor, etc.). Refer to Window Book's Postal Package Partner™ that has ZIP+4 address check which ensures your packages are delivered the first time.

ZIP+4 barcode—A nine-digit POSTNET barcode consisting of 52 vertical bars.

Zone Chart—The USPS Official National Zone Chart Data Program is administered from the National Customer Support Center (NCSC) in Memphis, TN. Single-page zone charts for originating mail are available at no cost from local post offices or online at

Zoned Rate—A rate structure for Priority Mail, Periodicals, Parcel Post, and Bound Printed Matter that is based on weight and distance traveled (or number of zones crossed).