# How our claims are verified

> How every claim on this site is verified: the twelve platforms we surveyed, how comparisons are sourced and re-checked, how honest open-tracking is measured.

Canonical: https://emailfast.dev/legal/claims-methodology

## The claims ledger

Every load-bearing factual statement on this site is a numbered entry in an internal
claims ledger, each carrying the exact evidence that backs it — a code path, a config
value, a test, or a policy page. Pages reference claims by id, and the site build
resolves them. The build **fails** if a page cites a claim the ledger doesn't recognize,
or uses a phrase we've told it we may not honestly make (for example, a certification we
don't hold or a metric we have no live history for). The marketing cannot ship ahead of
the product because the tooling won't let it.

## The platforms we surveyed

We reviewed these twelve against their own public pages in **July 2026**:

Mailchimp · Substack · beehiiv · Buttondown · Kit · Loops · SendGrid · Mailgun ·
Postmark · Resend · EmailJS · Paubox.

Two of our claims lean on this survey, and they range over different subsets — so we're
explicit about the scope of each:

- **"None offers customer-held encryption keys" (the keys claim).** A *negative*
  statement true across **all twelve** — none of them, whether a newsletter tool or a
  delivery API, offers customer-held keys for message content.
- **The rented-delivery claim.** This does **not** say every platform we surveyed rents
  its delivery — several of the twelve (SendGrid, Mailgun, Postmark, Resend) *are* the
  delivery infrastructure other senders rent from. It names **specific** consumer
  newsletter platforms whose own pages disclose an upstream provider — beehiiv (SendGrid),
  Buttondown (Mailgun/Postmark), Substack (Mailgun) — and mirrors each source exactly.

Our per-platform comparisons — honest about where each of them wins — are on the
[comparison pages](/compare).

## How comparative claims are sourced

- **Mirror the document, don't infer.** Each comparison is phrased to say what the
  source page says. "Buttondown's subprocessor list names Mailgun and Postmark" mirrors
  a document; we avoid inferences dressed as facts.
- **Scope and date are load-bearing.** Every comparative claim states the survey scope
  (the twelve above) and its verification date, so "every" can never quietly overreach.
- **Evidence captured.** Each comparative claim will be backed by an archived snapshot
  of the source page, captured and kept alongside its ledger entry, so a claim can be
  re-checked against exactly what the source said the day we verified it.
- **Quarterly re-verification.** Comparisons decay as platforms change, so they're
  re-checked each quarter and re-dated. When one is wrong, our
  [corrections policy](/legal/corrections) says how fast we fix it.

## How "open tracking that refuses to lie" is measured

open tracking that refuses to lie: privacy-proxy prefetch “opens” are detected and not counted as human reads. Concretely: a privacy proxy (Apple Mail Privacy Protection,
corporate scanners, link-prefetchers) fetches a tracking pixel automatically, without a
human ever opening the message. We classify an open as machine-generated when it carries
a known proxy/bot signature **or** lands within a short window of the send (before a
human plausibly could), and we exclude those from human open counts.

**Its error bounds, stated honestly.** This is best-effort classification, not
certainty. A new proxy we haven't catalogued can slip a machine open through until we
add its signature; an unusually fast genuine reader near the send can be over-excluded.
We tune the window and signatures from real traffic and would rather under-count a human
open than report a robot as a reader — the opposite of the industry default.

## Endorsements and material connections

We publish no customer quotes today. When we do, any quote or endorsement from a customer
who received free or discounted service (for example, an early design partner) will
disclose that connection plainly — because the honesty is the point, not an embarrassment.
That commitment is adopted now, before the first one ships.