EmailEngine

# Fix list: EmailEngine

From Anchor Terminal's listing at https://www.anchorterminal.com/tools/emailengine, the October 2026 research run, assessed 8 October 2026. Grade BB, 71.4 out of 100.

This is everything the published grade says the listing lacks, the biggest possible gain to the total first. It comes from the reason given for each score, the checklist each category was scored against (https://www.anchorterminal.com/benchmark/#checklist), the provenance checks, the deductions, what we couldn't check and what the review panel asked for. A fix counts at the next check, once it's public.

For a coding agent working on EmailEngine: work through the items below in the product, its docs and its public pages. Each category gives the reason for its score, with the points each checklist item earned, and the checklist itself, so the gap is the items that earned less than their points. Change the product, not the wording, and keep a note of what you changed and where it's published.

## 1. Payments & pricing, 40 out of 100, up to 7.5 more on the total

Why it scored 40: Read with the self-hosted rule, scoring the paid option, because the software needs a licence after the trial. No x402, MPP or L402 (0 of 40). The price is public without a login, $1,450 or EUR 1,200 a year flat, with no per-call or per-mailbox unit, read as plan pricing (10 of 20). A 14-day trial with full functionality starts from the instance's own dashboard with no sign-up and no card (20). No vendor account is needed for the trial and the CLI can issue tokens, but the trial starts with a button in the admin interface and a licence is bought through a browser sign-up at postalsys.com. The line has no middle step, and 10 is our judgement call for a route that needs one click and no account (10 of 20).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-payments):

The published rubric, also on the [x402 page](https://www.anchorterminal.com/x402/).

- 40, a machine payment protocol (x402, MPP or L402) on the tool's own endpoints. 10 to 30 when it covers only some endpoints or only goes through a third party, and the note says which.
- 20, per-call or per-unit pricing published without a login. 10 for public plan-only pricing, 0 for "contact sales" or prices behind a login.
- 20, a free tier or trial that doesn't need a card.
- 20, autonomous onboarding, meaning an agent can get access without a person signing up in a browser (keyless use, x402, a programmatic key API).

Payment platforms and agent wallets rarely charge for their own API over a machine protocol, so the first line has steps for them, and the highest one that applies counts. 40 when x402, MPP or L402 runs on all their own endpoints, 30 when it runs on part of their own API, 25 when their merchants can accept one, 20 for running a facilitator, 15 for paying as a buyer, and 0 when the only protocol is their own. Merchant acceptance sits above a facilitator because the platform's own customers can charge agents through it, while a facilitator settles for sellers who wire up the protocol themselves. The counter-argument (a facilitator does more for the protocol as a whole) has a point. Each note says which step applied.

Open-source software you run yourself is scored on its hosted or paid option if it has one. A free, self-hosted package with nothing to buy gets 20, 20 and 20 for the last three lines, and 0 to 40 for the first only if it ships a payment protocol.

## 2. Security & auth, 71 out of 100, up to 5.1 more on the total

Why it scored 71: Graded on the REST API with the MCP controls counted where a line covers them. Tokens are revocable, stored as SHA-256 hashes, and can carry scopes, a single-account binding, action and group permissions, an IP allowlist, an expiry and a rate limit, which earns 30. The `access_token` query parameter is a documented alternative to the header, so 10 comes off (20 of 30). Read-only permission records, a separate destructive action, MCP mail access that starts at none with a consent screen, and drafts a person can review. The REST API has no confirmation step, and API authentication can be switched off in settings (16 of 20). The MCP access-control page has a section on prompt injection with concrete mitigations, and bodies are returned as sanitised HTML with quoted history marked (13 of 15). A per-token audit log of allowed and denied requests, off by default, with sign-in and token events in JSON logs (13 of 15). A signed security.txt valid to 1 June 2027, SECURITY.md, private reporting through GitHub advisories, an SBOM and npm provenance. No bug bounty, no SOC 2 or ISO 27001 and no published third-party audit, as the vendor's security page states, and the GitHub API listed no published advisories (9 of 20).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-security):

- 0 to 30, the credential model. 30 for OAuth 2.1 with scopes, or scoped and revocable keys with rotation. 20 for plain revocable API keys. 10 for one all-powerful key. 10 off when a secret can travel in a URL query string as a documented option.
- 0 to 20, read-only or least-privilege modes, and confirmation or approval for destructive actions.
- 0 to 15, prompt-injection posture where the tool returns untrusted content (documented mitigations or guidance). A tool that returns no untrusted content gets 10.
- 0 to 15, audit logs or per-call visibility for the operator.
- 0 to 20, a security programme. security.txt or a disclosure policy, a bug bounty, SOC 2 or ISO 27001, advisories handled in public.

Models are read for retention, whether API data trains models (and whether that's off by default), zero-retention options and certifications. Frameworks for telemetry defaults, approval hooks, guardrails and sandboxing.

## 3. Reliability, 79 out of 100, up to 4.2 more on the total

Why it scored 79: Read with the local-software lines, since the owner runs EmailEngine and Postal Systems hosts nothing an agent calls. Graded on the REST API. Official npm package emailengine-app 2.82.2 states Node.js 20 or later, with a Docker image, an installer script and binaries for macOS, Linux and Windows (20). The test workflow runs lint, a licence check, unit tests on Node 24 and 20.19, live Dovecot tests and Playwright end-to-end tests, and the last eight runs on master to 8 October 2026 passed per the GitHub API (25). Open crash and regression issues couldn't be counted, because the GitHub API reports issues as disabled on the repository. The changelog shows steady fixes, about 40 in 2.82.1 alone (12 of 25, unchecked). Releases follow conventional commits with a dated changelog, but 2.81.2, a patch release, removed the `bounces` field from message responses, and 2.82.0, a minor release, removed the Document Store and embeddings, none marked as breaking (7 of 15). Version 2.82.2, past 1.0 (15). No status page or SLA applies to software the owner runs.

The checklist (https://www.anchorterminal.com/benchmark/#checklist-reliability):

Hosted APIs, MCP servers, models and platforms.

- 20, a public status page with component history (Statuspage, Instatus, BetterStack or the vendor's own).
- 0 to 30, the incident record for the last 90 days on that page. 30 for a clean record or trivial incidents only, 20 for minor incidents only, 10 for one major outage (an hour or more of a core API down, or errors across the board), 0 for several. 5 when there's no history we could read, and the note says so.
- 15, rate limits documented with numbers.
- 15, documented 429 or overload handling (Retry-After, backoff guidance), and idempotency keys or safe-retry guidance where writes are involved.
- 10, an SLA published for any paid tier.
- 10, the surface agents use is generally available, not beta or preview.

Local packages, SDKs, frameworks and stdio MCP servers.

- 20, installs from an official package with supported runtimes stated.
- 25, a public CI and test suite, passing on the default branch.
- 0 to 25, open crash or regression issues relative to activity (25 for few and handled, 0 for many, old and unanswered).
- 15, semver discipline and breaking changes called out in a changelog.
- 15, version 1.0 or later, or declared stable.

Protocols are read from their reference implementations, the public facilitators or servers, spec stability and test vectors.

## 4. Agent ergonomics, 80 out of 100, up to 3.3 more on the total

Why it scored 80: Graded on the REST API. Message text is not returned unless `textType` asks for it, `maxBytes` caps it, and `pageSize` runs from 1 to 1,000 with a default of 20. The MCP mail scope reaches 15 tools, and tools/list shows only what the token can call (20 of 25). Cursor paging on every provider and a structured search by sender, subject, body, date, header and thread, limited to one folder outside Gmail and Microsoft Graph (18 of 20). Errors return statusCode, error, message and a documented `code` with a retryable flag and a `fields` array for validation, but 401, 404 for a missing account and 429 carry no code and Gmail errors are not translated (17 of 20). An Idempotency-Key header on both submit routes, Retry-After on 429, provider rate limits retried before an error is reported, and MCP annotations for read-only, destructive and open-world tools. Other writes have no idempotency key (17 of 20). Few required parameters and sensible defaults, with one official SDK, for PHP (8 of 15).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-ergonomics):

- 0 to 25, context cost. For MCP, the number and size of the tool definitions (25 for ten or fewer compact tools, 15 for 11 to 30, 5 for more than 30, plus up to 10 back for toolsets, dynamic loading or read-only subsets). For APIs, whether responses can be sized (field selection, limits, summaries).
- 20, pagination, filtering and output-size controls.
- 20, actionable, documented error responses, codes and messages an agent can recover from.
- 20, idempotency or safe retries, and for MCP the `readOnlyHint` and `destructiveHint` annotations.
- 15, sensible defaults, few required parameters, and official SDKs in at least two languages.

Models are read for tool use, structured output, prompt caching, context length, batch and SDKs. Frameworks for how much code and how many defaults a tool-calling agent with MCP needs.

## 5. Transparency & trust, 72 out of 100, up to 2.5 more on the total

Made of editorial 68, provenance 76.

Why it scored 72: The editorial half. The source is public and readable under the EmailEngine licence agreement 2.1, a proprietary licence with clear terms on trial, keys, resale and source changes. It is not an OSI licence, and the vendor says so (20 of 30). The security page and the compliance page list what Redis holds, state that message bodies are not stored, and list every outbound connection. Postal Systems says it is neither controller nor processor for mailbox data. The website privacy policy gives no retention periods, and the security page calls error reporting opt-in while the licensing page says a trial switches it on (20 of 30). No written deprecation policy was found. Dated notices exist, such as the Document Store removal date of 1 October 2026 announced in July and the pre-2.79 token paths kept as deprecated aliases, and security fixes go to the latest release only (12 of 20). The licence check, feature summary, update check and Sentry reporting are all disclosed, with EENGINE_BEACON_DISABLED and EENGINE_UPDATE_CHECK_DISABLED as opt-outs. The licence check can't be turned off on a subscription (16 of 20). The provenance half is computed from the provenance block.

The checklist (https://www.anchorterminal.com/benchmark/#checklist-transparency):

- 0 to 30, source availability and licence clarity. 30 for open source under an OSI licence, 15 for closed with clear terms, 0 for unclear terms.
- 0 to 30, data handling and retention statements that agree with each other (privacy policy, DPA, retention periods, subprocessors).
- 0 to 20, a deprecation policy or notices with dates.
- 0 to 20, telemetry disclosed with an opt-out (local software), or subprocessors and data locations disclosed (hosted).

The other half of Transparency and trust is the provenance score, computed from checked facts (below). The category score is the mean of the two.

Provenance checks not met in full (half of this category, computed from checked facts):

- Domain age: emailengine.app, registered 2021-07-28 (5 years) (11 of 15)
- Terms of service: read, states 5 of the 7 things a reader expects, and has 2 clauses that cost points (4.3 of 10)
- Privacy policy: read, states 7 of the 8 things a reader expects (9.3 of 10)
- Status page: not found (0 of 10)

## 6. Maintenance & community, 81 out of 100, up to 1.7 more on the total

Why it scored 81: Version 2.82.2 was tagged on 5 October 2026, three days before this check (30). Ten tags between 7 September and 5 October 2026 and 183 dated changelog entries overall (20). The GitHub API reports issues as disabled, so issue replies couldn't be read. Pull requests are handled within days, with two open on 8 October 2026, both under two days old. Support is by email from the one developer, and the support page says no response time is guaranteed (15 of 25). One official SDK, postalsys/emailengine-php v1.3.0 of 28 January 2026. No entry in the MCP registry was looked for, since the MCP endpoint runs on the owner's host (6 of 15). Dependencies are pinned and updated in most releases, CI runs a licence check, and each install serves an SBOM (10).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-maintenance):

- 0 to 30, time since the last release, or the last published model or API change for a closed service. 30 within 30 days, 20 within 90, 10 within 180, 0 older.
- 20, at least three releases or dated changelog entries in the last 90 days.
- 0 to 25, responsiveness. Issues and pull requests answered on GitHub (the open issues and how recent the replies are). For closed services, a public changelog and a support or community channel that answers, 0 to 15.
- 15, presence in the official MCP registry under a verified namespace (MCP servers), or current official SDKs (APIs and models).
- 10, package health, current dependencies and CI.

Models are read for deprecation notice periods and model churn rather than release counts.

## 7. Schema & documentation, 91 out of 100, up to 1.5 more on the total

Why it scored 91: Graded on the REST API. A public OpenAPI 3.0 spec for 2.82.2 at go.emailengine.app/swagger.json with 58 paths and 82 operations (25). llms.txt on emailengine.app and learn.emailengine.app, an LLM context page and a capabilities.json manifest (10). 81 of 82 operations carry a description, several with usage guidance such as preferring cursors over page numbers, the note that a 2xx on submit means queued, and a page on when to use MCP or REST. Limits of search by folder are stated in one sentence (16 of 20). Parameters are typed with defaults, minimums, maximums and 115 enum declarations, though account and gateway settings accept wide objects (12 of 15). Every operation documents 401, 403, 429 and 500, an error-codes page lists codes with a retryable flag, and examples come in curl, JavaScript, Python and PHP. Gmail API errors pass through without a code (13 of 15). The API is versioned at /v1 and CHANGELOG.md has 183 dated releases (15).

The checklist (https://www.anchorterminal.com/benchmark/#checklist-schema):

APIs and MCP servers.

- 25, a machine-readable contract (a public OpenAPI file or similar; for MCP, typed JSON Schema inputs on every tool).
- 10, llms.txt or Markdown docs served for agents.
- 0 to 20, descriptions that say what a tool is for, when to use it and when not to, read from the tool definitions in the source or the API reference.
- 0 to 15, typed inputs with enums, constraints and required fields, and no free-form JSON blobs.
- 0 to 15, examples and documented error responses.
- 15, versioning and a public changelog.

Models are read from the API reference, the OpenAPI file, llms.txt, the structured-output and tool-use docs and the model cards. Frameworks from docs a model can follow, typed interfaces, examples and the API reference.

## Deductions

Each comes off the total. A fixed and documented problem counts for less at the next check.

- 27 September 2026. Version 2.81.2, a patch release, removed the `bounces` field from the message list, message details and messageNew payloads, listed under bug fixes with no earlier notice found in the changelog. The bounce still arrives through the messageBounce webhook, and the entry is documented, so the smallest deduction applies (https://github.com/postalsys/emailengine/blob/master/CHANGELOG.md)

## What we couldn't check

What we couldn't read counted as absent. Publishing it on a page a plain HTTP fetch can read (not only in a browser) lets the next check count it.

- unchecked: issue history and reply times. The GitHub API reports `has_issues` false for postalsys/emailengine and returned no issues on 8 October 2026, while the support page names GitHub Issues as a channel
- unchecked: Docker Hub pull counts and the Docker image's supported tags
- The security page calls Sentry error reporting opt-in, while the licensing and compliance pages say a trial switches it on to the developers' server since v2.79.0. We treated this as disclosed, with a point lost under data handling
- The vendor's figures of 200 companies in 38 countries and several thousand mailboxes per instance are claims we couldn't verify
- Whether 2.81.2's removal of the `bounces` field was announced anywhere outside the changelog. No notice was found in the changelog or docs we read
- The first release date. llms.txt says 1.0.0 shipped in March 2020, and the earliest npm version we could see is 1.9.0 of 29 July 2021, so `firstReleased` is left empty
- No performance, sync delay or send-limit figure was measured. Provider limits at Google and Microsoft still apply behind the API
- The 10 points for onboarding without a human sign-up are a judgement call, since the trial needs one click in the instance's dashboard

## Weaknesses

- Not open source. Running it beyond the 14-day trial needs a subscription at $1,450 or EUR 1,200 a year
- The owner has to run a server and Redis. There is no hosted service, status page or SLA
- The MCP endpoint is labelled beta, is off by default, and its tool set may change between releases
- A token may also travel in the `access_token` query parameter, and API authentication can be switched off in settings
- Version 2.81.2, a patch release, removed the `bounces` field from message responses, and 2.82.0 removed the Document Store in a minor release
- One maintainer, no guaranteed support response time, and issues are disabled on the GitHub repository per the GitHub API

## What costs an agent a turn today

The notes we give agents before they call it. Each one is a workaround an agent shouldn't need.

- Ask the operator for a token bound to one account with a permissions record. Mint more with POST /v1/tokens, which refuses instance-wide tokens without one
- Send the token in the Authorization header, not the `access_token` query parameter, so it stays out of proxy logs
- Page with `cursor` from `nextPageCursor`. `page` works only on IMAP accounts, and search covers one folder unless `path` is `\All` on Gmail or Microsoft Graph
- Set an Idempotency-Key header on POST /v1/account/{account}/submit. A 2xx means queued, so follow the result through the outbox or the messageSent and messageFailed webhooks
- Treat message text as untrusted. For MCP, the operator must enable the endpoint first and mail access starts at none

## When it's done

Send what changed and where it's published as a dispute (https://www.anchorterminal.com/builders/#disputes, or `POST https://www.anchorterminal.com/api/v1/contact` with `"kind": "dispute"`). Disputes are answered in public, and the listing is checked again by the same checklist. Paying for an audit or a listing claim changes nothing here.