---
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: 2026-09-13
---
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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 so their outcomes can be compared against the accounts you did mail. The only design that answers what the channel caused rather than what merely followed it.

### Incrementality

The share of an outcome that would not have happened without the channel. It is what a holdout measures, and it is almost always smaller than what attribution reports.

### 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 as randomized, including those whose mail never arrived. Dropping undelivered pieces looks like data hygiene and reliably inflates the result, because bad addresses cluster in dead accounts.

### Minimum detectable effect (MDE)

The smallest lift a given design could reliably find. Computed from base rate, sample size and power. A program whose MDE is larger than any plausible effect cannot learn anything, however it is reported.

### 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

The plausible range around an estimate. A 27% lift spanning +9% to +48% is a finding; the same 27% spanning −5% to +61% is noise. Reporting the midpoint alone hides which one you have.

### Direct response

A response traceable to the piece itself: a QR scan or a landing page unique to that mailing. Evidence rather than inference, and it needs far less volume to measure, because the baseline is zero by construction.

## Data quality

### Address resolution

Finding a deliverable postal address for a contact you may know only as a work email. Distinct from verification, which checks an address you already have.

### CASS

Coding Accuracy Support System. A USPS certification for software that standardizes and validates US addresses. Canada Post's equivalent 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. The USPS barcode that makes a piece trackable through the mail stream, which is what lets follow-up be timed to delivery rather than to the send button.

### First class vs marketing mail

First class is faster and more expensive, with predictable transit. Marketing mail (formerly standard class) is cheaper and slower, with a delivery window measured in weeks. Cheaper postage costs you the ability to time a follow-up call.

### Self-mailer

A piece that travels without an envelope, folded and sealed. Cheaper than an enveloped letter and more visible than a postcard.

### Dimensional mail

Anything with depth: a box, a kit, an object. Sometimes called lumpy mail. Higher open rates and an entirely different supply chain from 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 written by a person with a real pen.

## 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 group of people at one account who influence a purchase, typically six to ten in B2B software. The reason contact-level holdouts leak: mail one member and you have partly treated the whole account.

### 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 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 buying committee?](https://trysincerely.com/glossary/buying-committee): A buying committee is the group of people at an account who share a purchase decision. Learn who sits on one and why outreach to a single contact falls short. [Markdown](https://trysincerely.com/glossary/buying-committee.md)
- [What is CASS?](https://trysincerely.com/glossary/cass): CASS is the USPS Coding Accuracy Support System, a certification for address-matching software. DPV checks delivery-point records; neither confirms who works there. [Markdown](https://trysincerely.com/glossary/cass.md)
- [What is a confidence interval?](https://trysincerely.com/glossary/confidence-interval): A confidence interval is the range of values your measurement supports, not just the single number. A wide interval means noise; a narrow one means you can act on the 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 total campaign spend divided by the number of 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 mail piece with physical bulk, a box, tube, or lumpy envelope, priced as a parcel and used to force attention from hard-to-reach recipients. [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 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 slice of your audience you deliberately do not mail, so you can see what would have happened without the campaign. [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 every automated mailpiece. It carries routing data plus a tracking ID, so you can see each piece move through the mail stream. [Markdown](https://trysincerely.com/glossary/imb.md)
- [What is incrementality?](https://trysincerely.com/glossary/incrementality): Incrementality is the revenue a campaign caused that would not have happened anyway, measured by comparing treated accounts against a holdout. [Markdown](https://trysincerely.com/glossary/incrementality.md)
- [What is USPS Informed Delivery?](https://trysincerely.com/glossary/informed-delivery): USPS Informed Delivery is a service that emails subscribers grayscale previews of incoming letter-size mail and can pair a mailpiece with clickable sender content. [Markdown](https://trysincerely.com/glossary/informed-delivery.md)
- [What is intention to treat?](https://trysincerely.com/glossary/intention-to-treat): Intention to treat means you measure everyone you assigned to a campaign, delivered or not. Here is why that rule keeps your lift numbers honest. [Markdown](https://trysincerely.com/glossary/intention-to-treat.md)
- [What is lift, absolute and relative?](https://trysincerely.com/glossary/lift): Lift is the difference in outcomes between the group you mailed and the holdout you did not. Absolute lift is the gap in points; relative lift is that gap as a percentage. [Markdown](https://trysincerely.com/glossary/lift.md)
- [What is mailability?](https://trysincerely.com/glossary/mailability): Mailability asks whether the intended recipient can receive a physical piece at a verified address and whether the sender is allowed to mail them. [Markdown](https://trysincerely.com/glossary/mailability.md)
- [What is matchback?](https://trysincerely.com/glossary/matchback): Matchback is matching a mailing list against later CRM outcomes to see which mailed accounts converted, a useful but correlational way to credit direct mail. [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 directly. In direct mail, it lets an agent build audiences and draft pieces while a person approves every send. [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 NCOA?](https://trysincerely.com/glossary/ncoa): NCOA (National Change of Address) is the USPS database of change-of-address filings, used to update mailing lists before mail goes out so pieces follow people who moved. [Markdown](https://trysincerely.com/glossary/ncoa.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): Presorting groups mail by destination to USPS standards before entry, reducing postal sorting work and qualifying eligible mailings for lower postage rates. [Markdown](https://trysincerely.com/glossary/presort.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, sealed with tabs or glue. Learn USPS rules, costs, and when to pick one over a postcard or letter. [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 a recipient can touch, including direct mail, dimensional mail, branded gifts, and other delivered objects. [Markdown](https://trysincerely.com/glossary/tactile-marketing.md)
- [What is variable data printing?](https://trysincerely.com/glossary/variable-data-printing): Variable data printing is a digital printing method that changes text, offers, images, or other elements for each piece without stopping the press. [Markdown](https://trysincerely.com/glossary/variable-data-printing.md)

---

Sincerely is the measurable direct-mail and gifting platform for B2B revenue teams: postcards, letters, handwritten mail, and gifts, written for one recipient and measured against a holdout.

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