---
title: "Glossary"
description: "Plain definitions for the terms that come up when you run direct mail as a measured channel: holdouts, incrementality, matchback, intention to treat, CASS, NCOA, IMb, and the rest."
canonical: https://trysincerely.com/glossary
last_updated: 2026-10-18
---
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# Glossary

> Plain definitions for the terms that come up when you run direct mail as a measured channel: holdouts, incrementality, matchback, intention to treat, CASS, NCOA, IMb, and the rest.

Source: https://trysincerely.com/glossary

## The words, defined plainly.

Direct mail carries a lot of vocabulary, some of it postal, some of it statistical, and some of it invented by vendors to make attribution sound like proof. These are the terms that come up when mail is run as a measured channel, defined the way we use them.

## Measurement

### Holdout

A group of accounts deliberately excluded from a campaign. Random assignment lets you compare their outcomes with mailed accounts and estimate what the channel caused, subject to sampling uncertainty and a sound experiment design.

### Incrementality

The additional outcomes attributable to a campaign beyond what would have happened without it. A randomized holdout helps estimate that difference; ordinary attribution assigns credit without establishing causation. In depth: [Attribution vs incrementality](https://trysincerely.com/guides/attribution-vs-incrementality).

### Lift, absolute and relative

Absolute lift is the difference in percentage points: 8.9% against 7.0% is 1.9 points. Relative lift expresses the same gap as a proportion: 27%. Absolute is what converts to pipeline; relative is what appears in marketing.

### Matchback

Joining closed opportunities back to the accounts that were mailed. Useful for sizing a program, but silent on causation, because it has no comparison group.

### Attribution window

The period after delivery during which an outcome is counted as related to the piece. Longer windows credit the channel with more, which is why the window has to be fixed before the campaign runs.

### Intention to treat

Analyzing every account in its randomized group, including those whose mail never arrived. Excluding accounts after assignment can break the original comparison and bias the result. Delivery failures belong in the program's measured outcome.

### Minimum detectable effect (MDE)

The smallest effect a design is planned to detect at a chosen power and significance threshold. It depends on the base rate, sample size, and group allocation. Smaller effects may remain unresolved, while descriptive and operational results can still be useful.

### Statistical power

The probability a test detects a real effect of a given size. Conventionally 80%. Low power produces null results that get misread as evidence the channel failed.

### Confidence interval

A range of effects compatible with the data. A 27% lift with an interval of +9% to +48% is a finding. The same 27% with an interval of −5% to +61% cannot rule out no effect. Reporting the midpoint alone hides which one you have.

### Direct response

A recorded action through a piece-specific response path, such as a QR code or short link. It identifies the source link, not necessarily the visitor or the cause of a later purchase. Forwarded links and automated visits require care.

## Data quality

### Address resolution

Finding the most likely current mailing location for a person or business. Distinct from postal verification, which checks the address itself. A real headquarters can still be the wrong location for the intended recipient.

### CASS

Coding Accuracy Support System. A USPS certification for address-matching software. The separate Delivery Point Validation result checks whether an address is represented in the USPS delivery file. Neither establishes who lives or works there. Canada Post's equivalent certification is SERP.

### NCOA

National Change of Address. A USPS dataset of forwarding orders, used to update addresses for people and businesses that have moved.

### Mailability

Whether a given address is fit to receive a piece before you buy postage: format valid, deliverable, not suppressed, and confident enough to be worth the spend.

### Suppression list

A durable do-not-mail decision applied across future sends. Unlike a temporary campaign exclusion, it survives imports, syncs, and new campaigns.

### Return to sender

A piece the postal service could not deliver and sent back. Costly, but the most useful feedback a mail program gets: every return is a labeled example that improves the next address decision.

## Production

### IMb

Intelligent Mail barcode. USPS equipment scans it as eligible mail moves through the network. The scan trail supports delivery estimates and follow-up timing, but does not prove a handoff to the recipient or that the piece was read.

### First class vs marketing mail

USPS sets 1 to 5 days for First-Class Mail and 4 to 7 days for Marketing Mail sent across the network. These are service standards, not delivery guarantees. First-Class includes forwarding and return service; Marketing Mail generally requires an extra service endorsement for either.

### Self-mailer

A folded and sealed piece that travels without an envelope. It offers several panels for content. Production costs and postal eligibility depend on the dimensions, stock, folds, and sealing method.

### Dimensional mail

A physical send with bulk, such as a box, kit, tube, or an envelope containing an object. It can require parcel postage, packing, and fulfillment beyond ordinary flat print.

### Robotic handwriting

A machine holding a real ballpoint pen, writing in a handwriting style. Not a printed font that imitates handwriting, and not a person. Sincerely’s handwritten mail is genuinely written by hand.

## Programs

### ABM

Account-based marketing. Treating a named list of accounts as the unit of targeting and measurement rather than individual leads. Mail fits it well, and it is also why holdouts have to be assigned by account.

### Buying committee

The people at one account who influence a purchase, including users, evaluators, budget owners, and approvers. The size varies by purchase. Contact-level holdouts can leak when a mailed committee member shares the message with an unmailed colleague.

### Signal

A public or CRM event that makes an account worth mailing now: a funding round, a job posting, a renewal window, a stalled deal. What separates a campaign from a batch send.

### Cost per opportunity

Program cost divided by incremental opportunities created. The unit that decides whether a channel gets funded again, and the reason cost per piece is the wrong comparison.

### Provenance

The record of where a claim in a piece came from and when. On paper it matters more than in email, because a letter with a wrong fact about a company's funding round cannot be recalled.

The [holdout testing guide](https://trysincerely.com/holdout-testing) covers the measurement terms in depth, and the [measurement page](https://trysincerely.com/measurement) shows how they appear in a real report.

## Every page in this collection

- [What is ABM (account-based marketing)?](https://trysincerely.com/glossary/abm): ABM (account-based marketing) targets a named list of accounts worth winning, instead of casting wide for any lead who fits a profile. [Markdown](https://trysincerely.com/glossary/abm.md)
- [What is an add-on acquisition?](https://trysincerely.com/glossary/add-on-acquisition): An add-on acquisition is a company bought by a business that a private equity firm already owns. How add-ons differ from platforms, and how sponsors find them. [Markdown](https://trysincerely.com/glossary/add-on-acquisition.md)
- [What is address resolution?](https://trysincerely.com/glossary/address-resolution): Address resolution finds the most likely current mailing location for a person or business before postal verification checks the address itself. [Markdown](https://trysincerely.com/glossary/address-resolution.md)
- [What is an attribution window?](https://trysincerely.com/glossary/attribution-window): An attribution window is the fixed period after a mail piece lands during which an outcome, like a meeting or an opportunity, counts as caused by the campaign. [Markdown](https://trysincerely.com/glossary/attribution-window.md)
- [What is a bulk mail permit?](https://trysincerely.com/glossary/bulk-mail-permit): A bulk mail permit lets a business pay USPS postage from an account instead of stamps. As of October 2026 it costs $390 to apply and $390 a year. [Markdown](https://trysincerely.com/glossary/bulk-mail-permit.md)
- [What is business reply mail (BRM)?](https://trysincerely.com/glossary/business-reply-mail): Business reply mail is a USPS reply card or envelope that needs no stamp. The sender pays postage plus a fee only for the pieces that come back. [Markdown](https://trysincerely.com/glossary/business-reply-mail.md)
- [What is a buying committee?](https://trysincerely.com/glossary/buying-committee): A buying committee is the group of people at an account who share a purchase decision. Outreach to one contact misses the rest. [Markdown](https://trysincerely.com/glossary/buying-committee.md)
- [What is a carrier route?](https://trysincerely.com/glossary/carrier-route): A carrier route is the set of addresses one USPS carrier delivers to. Sorting mail to a route earns the lowest Marketing Mail prices and is how EDDM works. [Markdown](https://trysincerely.com/glossary/carrier-route.md)
- [What is CASS?](https://trysincerely.com/glossary/cass): CASS is the USPS certification for address-matching software. DPV checks delivery-point records, and neither one confirms who works at the address. [Markdown](https://trysincerely.com/glossary/cass.md)
- [What is a confidence interval?](https://trysincerely.com/glossary/confidence-interval): A confidence interval describes uncertainty around an estimate. Its width, direction, assumptions and business value all matter when acting on a result. [Markdown](https://trysincerely.com/glossary/confidence-interval.md)
- [What is cost per opportunity?](https://trysincerely.com/glossary/cost-per-opportunity): Cost per opportunity is campaign spend divided by the new sales opportunities it created. It ties channel cost to pipeline, not clicks or replies. [Markdown](https://trysincerely.com/glossary/cost-per-opportunity.md)
- [What is dimensional mail?](https://trysincerely.com/glossary/dimensional-mail): Dimensional mail is any piece with physical bulk: a box, tube, or lumpy envelope. The postal service prices it as a parcel, not a letter. [Markdown](https://trysincerely.com/glossary/dimensional-mail.md)
- [What is direct response?](https://trysincerely.com/glossary/direct-response): Direct response is marketing built to trigger a measurable action now, like a scan, reply, or booked meeting, so every dollar can be traced to a result. [Markdown](https://trysincerely.com/glossary/direct-response.md)
- [What is DPV (Delivery Point Validation)?](https://trysincerely.com/glossary/dpv): DPV checks whether an address is a known USPS delivery point. Here is what its Y, D, S and N codes mean and what the vacant and CMRA flags tell you. [Markdown](https://trysincerely.com/glossary/dpv.md)
- [What is a direct mail drop date?](https://trysincerely.com/glossary/drop-date): A direct mail drop date is the date a finished mailing enters the postal stream, not the date recipients are expected to receive it. [Markdown](https://trysincerely.com/glossary/drop-date.md)
- [What is first-class mail vs marketing mail?](https://trysincerely.com/glossary/first-class-vs-marketing-mail): The difference between USPS First-Class Mail and Marketing Mail, and why B2B senders usually pay for First-Class. [Markdown](https://trysincerely.com/glossary/first-class-vs-marketing-mail.md)
- [What is a holdout?](https://trysincerely.com/glossary/holdout): A holdout is the group you deliberately do not mail. Comparing them to the mailed group shows what the campaign actually caused. [Markdown](https://trysincerely.com/glossary/holdout.md)
- [What is an IMb (Intelligent Mail barcode)?](https://trysincerely.com/glossary/imb): The IMb is the 65-bar USPS barcode on automated mail. It carries routing data and a tracking ID so you can follow a piece through the mail. [Markdown](https://trysincerely.com/glossary/imb.md)
- [What is a postage indicia?](https://trysincerely.com/glossary/indicia): A postage indicia is the printed mark that shows postage was paid through a USPS permit, so bulk mail needs no stamp. What it says and where it goes. [Markdown](https://trysincerely.com/glossary/indicia.md)
- [What is USPS Informed Delivery?](https://trysincerely.com/glossary/informed-delivery): USPS Informed Delivery emails subscribers preview images of incoming letter mail and lets senders attach a clickable link to each piece. [Markdown](https://trysincerely.com/glossary/informed-delivery.md)
- [What is intention to treat?](https://trysincerely.com/glossary/intention-to-treat): Intention to treat analyzes accounts in their randomized groups, delivered or not. It preserves assignment and avoids bias from post-launch exclusions. [Markdown](https://trysincerely.com/glossary/intention-to-treat.md)
- [What is lift, absolute and relative?](https://trysincerely.com/glossary/lift): Lift is the outcome difference between mailed accounts and the holdout. Absolute lift is percentage points; relative lift is percent change. [Markdown](https://trysincerely.com/glossary/lift.md)
- [What is mailability?](https://trysincerely.com/glossary/mailability): Mailability checks whether a recipient can receive mail at a verified address and whether the sender has legal permission to mail them. [Markdown](https://trysincerely.com/glossary/mailability.md)
- [What is matchback?](https://trysincerely.com/glossary/matchback): Matchback links mailed accounts to later CRM conversions. It shows correlation but cannot prove the mail caused the outcome. [Markdown](https://trysincerely.com/glossary/matchback.md)
- [What is MCP (Model Context Protocol)?](https://trysincerely.com/glossary/mcp): MCP is the open protocol that lets an AI agent call another product's tools. In direct mail it builds audiences and drafts copy for human approval. [Markdown](https://trysincerely.com/glossary/mcp.md)
- [What is minimum detectable effect (MDE)?](https://trysincerely.com/glossary/minimum-detectable-effect): Minimum detectable effect is the smallest lift your test can reliably detect given its sample size, holdout split, and baseline rate. [Markdown](https://trysincerely.com/glossary/minimum-detectable-effect.md)
- [What is the USPS Move Update requirement?](https://trysincerely.com/glossary/move-update): Move Update requires lists mailed at commercial First-Class or Marketing Mail prices to be checked for filed moves within 95 days before mailing. [Markdown](https://trysincerely.com/glossary/move-update.md)
- [What is NCOA?](https://trysincerely.com/glossary/ncoa): NCOA is the USPS database of change-of-address filings, used to update a mailing list before mail goes out so pieces follow the people who moved. [Markdown](https://trysincerely.com/glossary/ncoa.md)
- [What is the nonmachinable surcharge?](https://trysincerely.com/glossary/nonmachinable-surcharge): USPS adds $0.49 to a single-piece letter its machines cannot sort, such as a square card or a lumpy envelope. What triggers it, as of October 2026. [Markdown](https://trysincerely.com/glossary/nonmachinable-surcharge.md)
- [What determines direct mail postage rates?](https://trysincerely.com/glossary/postage-rates): Direct mail postage rates depend on mail class, shape, weight, presort depth, and where the mailing enters the USPS network. [Markdown](https://trysincerely.com/glossary/postage-rates.md)
- [What is presort mail?](https://trysincerely.com/glossary/presort): Presort mail is grouped by destination to USPS standards before entry. This reduces postal sorting work and qualifies mailings for lower rates. [Markdown](https://trysincerely.com/glossary/presort.md)
- [What is proprietary deal flow?](https://trysincerely.com/glossary/proprietary-deal-flow): Proprietary deal flow is acquisitions a buyer finds by reaching owners directly, before an advisor runs a competitive sale. What it means and how it is built. [Markdown](https://trysincerely.com/glossary/proprietary-deal-flow.md)
- [What is provenance?](https://trysincerely.com/glossary/provenance): Provenance is the recorded origin of a data point, the source and date behind an address or account fact, so you can judge whether to trust it before you print. [Markdown](https://trysincerely.com/glossary/provenance.md)
- [What is a PURL?](https://trysincerely.com/glossary/purl): A PURL is a unique URL printed on one mail piece. The token ties a visit to that piece and its intended recipient, but it does not verify who opened it. [Markdown](https://trysincerely.com/glossary/purl.md)
- [What is return to sender?](https://trysincerely.com/glossary/return-to-sender): Return to sender is mail the USPS could not deliver and sent back, usually because the address is wrong, the recipient moved, or the piece was refused. [Markdown](https://trysincerely.com/glossary/return-to-sender.md)
- [What is robotic handwriting?](https://trysincerely.com/glossary/robotic-handwriting): Robotic handwriting is mail written by a machine holding a real pen, so each piece looks hand-penned at scale. Here is how it works and when it beats print. [Markdown](https://trysincerely.com/glossary/robotic-handwriting.md)
- [What is a seed list in direct mail?](https://trysincerely.com/glossary/seed-mailing): A direct mail seed list adds controlled postal addresses to a real campaign so the sender can inspect what arrived, where it arrived, and when. [Markdown](https://trysincerely.com/glossary/seed-mailing.md)
- [What is a self-mailer?](https://trysincerely.com/glossary/self-mailer): A self-mailer is a folded printed piece that mails without an envelope. USPS rules, costs, and use cases compared to postcards and letters. [Markdown](https://trysincerely.com/glossary/self-mailer.md)
- [What is a signal?](https://trysincerely.com/glossary/signal): A signal is an observable event that suggests an account is worth contacting right now, like a funding round, a new executive, or a burst of hiring. [Markdown](https://trysincerely.com/glossary/signal.md)
- [What is statistical power?](https://trysincerely.com/glossary/statistical-power): Statistical power is the probability your test detects a real effect. Learn why underpowered direct mail tests waste money and how to size a holdout correctly. [Markdown](https://trysincerely.com/glossary/statistical-power.md)
- [What is a suppression list?](https://trysincerely.com/glossary/suppression-list): A suppression list is a durable do-not-contact record checked before every send. Learn what belongs on one, how exclusions differ, and why deletion fails. [Markdown](https://trysincerely.com/glossary/suppression-list.md)
- [What is tactile marketing?](https://trysincerely.com/glossary/tactile-marketing): Tactile marketing is physical marketing: direct mail, dimensional mail, branded gifts, and other delivered objects. [Markdown](https://trysincerely.com/glossary/tactile-marketing.md)
- [What is UAA mail (undeliverable as addressed)?](https://trysincerely.com/glossary/uaa): UAA is the USPS term for mail it cannot deliver as addressed. Learn the usual causes, what happens to each mail class, and what endorsements change. [Markdown](https://trysincerely.com/glossary/uaa.md)
- [What is variable data printing?](https://trysincerely.com/glossary/variable-data-printing): Variable data printing changes text, images, and offers for each piece without stopping the press. How it works for account-based mail. [Markdown](https://trysincerely.com/glossary/variable-data-printing.md)
- [What is a ZIP+4 code?](https://trysincerely.com/glossary/zip-plus-4): A ZIP+4 code adds four digits to a ZIP Code to narrow mail to a few streets or one building. Two more digits mark the exact delivery point. [Markdown](https://trysincerely.com/glossary/zip-plus-4.md)

---

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