Outlook Mail (Microsoft Graph)

# Fix list: Outlook Mail (Microsoft Graph)

From Anchor Terminal's listing at https://www.anchorterminal.com/tools/outlook-mail-graph, the October 2026 research run, assessed 8 October 2026. Grade B, 66.3 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 Outlook Mail (Microsoft Graph): 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, 35 out of 100, up to 8.1 more on the total

Why it scored 35: No x402, MPP or L402 (0). Mail endpoints aren't on the metered API list, so calls carry no charge, but a work mailbox needs an Exchange Online or Microsoft 365 licence and the plan price page refused our reader (15). Personal Outlook.com accounts work with delegated Mail permissions at no cost and no card (20). A person registers an app in Entra and, for application permissions, an admin consents (0).

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. Reliability, 60 out of 100, up to 8 more on the total

Why it scored 60: Graded on the v1.0 REST API. A public Microsoft service health page at status.cloud.microsoft (20). It renders only with JavaScript, so we couldn't read components or history (5). Outlook limits are published at 10,000 requests per 10 minutes, four concurrent requests and 150 MB of uploads per 5 minutes for each app and mailbox pair, and Exchange Online caps sending at 30 messages a minute and 10,000 recipients a day (15). 429 responses carry `Retry-After`, with backoff guidance and SDK retry handlers, but sendMail has no idempotency key and returns 202 Accepted before delivery, so a retried send can duplicate (10 of 15). No SLA covering the Graph API was found in the pages we could read, and the Online Services SLA page refused our reader (0). Mail endpoints are generally available on v1.0 (10).

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.

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

Why it scored 71: OAuth 2.0 through Microsoft Entra ID with delegated and application permissions, from Mail.ReadBasic through Mail.Read and Mail.ReadWrite to a separate Mail.Send (30). Mail.ReadBasic leaves out body, preview and attachments, Mail.ReadWrite doesn't include sending, and RBAC for Applications in Exchange Online limits an application permission to chosen mailboxes. Nothing asks for confirmation before a send or delete (17). Message bodies written by outside senders reach the caller, and no injection guidance was found in the mail reference or the Mail MCP reference (0). Graph activity logs record app, user, IP address, request URI and scopes, but need Entra ID P1 or P2 and an Azure log destination (12). microsoft.com's security.txt names the MSRC report portal, a bounty policy and a disclosure policy but passed its Expires date on 23 September 2026, Office 365 has a SOC 2 Type 2 report, and a token-leak fix in the JavaScript client sits unreleased with no advisory (12).

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.

## 4. Agent ergonomics, 81 out of 100, up to 3.1 more on the total

Why it scored 81: `$select`, `$top`, `bodyPreview` (255 characters), `uniqueBody` and `Prefer: outlook.body-content-type="text"` keep message payloads small (23). `@odata.nextLink` paging with pages of 1 to 1,000, `$filter`, `$orderby`, `$search` and per-folder delta queries (20). Errors carry a code, message and request ID, and named codes such as `InefficientFilter` say what to change (17). Immutable IDs through a `Prefer` header and `If-Match` on updates help safe retries, but sendMail, reply and forward have no idempotency key, and the preview Mail MCP reference lists no readOnlyHint or destructiveHint annotations (8). Official SDKs in C#, Java, Go, PHP, Python, PowerShell and TypeScript, though the JavaScript client on npm is 3.0.7 from September 2023 (13).

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, 75 out of 100, up to 2.2 more on the total

Made of editorial 65, provenance 85.

Why it scored 75: Closed service under the Microsoft APIs terms of use, last updated October 2025, with MIT SDKs (15). Microsoft 365's retention page says deleted customer content is removed within 30 days and within 180 days of a subscription ending, and the Exchange Online residency page names where mailbox content is stored. The privacy statement refused our reader and we didn't read the data protection addendum (20). A written policy of at least 24 months' notice before a v1.0 API or version is retired, and dated notices such as the Exchange Web Services retirement (20). Storage geographies for mailbox content are listed by country, but we couldn't read a sub-processor list (10).

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):

- Terms of service: read, states 5 of the 7 things a reader expects, and has 3 clauses that cost points (2.3 of 10)
- Privacy policy: read, states 8 of the 8 things a reader expects, and has 1 clause that costs points (8 of 10)
- security.txt: published but past its Expires date (5 of 10)

## 6. Maintenance & community, 76 out of 100, up to 2.1 more on the total

Why it scored 76: msgraph-sdk-python v1.64.0 on 6 October 2026 (30). Eight Python SDK tags since 10 July 2026, from v1.59.0 to v1.64.0 (20). A public changelog, a What's new page updated on 8 October 2026 and SDK issue trackers, but a security fix merged into the JavaScript client on 16 June 2026 still hasn't reached npm, and the changelog feed's newest entry is 3 August 2026 (10). Current SDKs in most languages, with the JavaScript client the exception at 3.0.7 (10). Active tagging on the Python repository, none of it reaching the JavaScript package (6).

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, 93 out of 100, up to 1.1 more on the total

Why it scored 93: OpenAPI for all of Graph v1.0 in microsoftgraph/msgraph-metadata (25). No llms.txt on learn.microsoft.com, but every reference page we asked for with `Accept: text/markdown` came back as Markdown (10). Reference pages state the purpose of each call, list permissions from least to most privileged and name limits such as the `$filter` and `$orderby` ordering rule and the 1,000-result cap on `$search` (17). Typed properties and enumerations in the metadata, though sendMail also accepts a base64 MIME blob (13). An example request and response on each page, a shared error format and a status code table, with few mail-specific error codes listed (13). v1.0 and beta, a dated changelog and a monthly What's new page updated on 8 October 2026 (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.

- 2026-06-16: a fix for a token leak through URL userinfo host confusion was merged into msgraph-sdk-javascript and the version bumped to 3.0.8, but on 8 October 2026 npm still serves 3.0.7 from September 2023 and the repository has no published advisory. Exploiting it needs an attacker-influenced URL passed to the client (https://github.com/microsoftgraph/msgraph-sdk-javascript/commit/5438ae90f50ef15d3656f0cf9c5485deee351f19, https://registry.npmjs.org/@microsoft/microsoft-graph-client/latest)

## 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: status page components and incident history, which need JavaScript
- unchecked: the Online Services SLA and Exchange Online plan prices, because www.microsoft.com answered our reader with 403
- unchecked: the Microsoft privacy statement, the MSRC bounty pages, the data protection addendum and the Microsoft 365 sub-processor list, which refused our reader or weren't found
- Whether Microsoft will publish msgraph-sdk-javascript 3.0.8 or an advisory for the 16 June 2026 fix
- Whether the Mail MCP tools carry readOnlyHint or destructiveHint annotations. The reference lists none
- The changelog feed's newest entry is 3 August 2026 while the What's new page was updated on 8 October 2026. We didn't establish why the feed stops there
- lastRelease is the Python SDK release of 6 October 2026. The newest mail entry on What's new that is generally available is dated only August 2026

## Weaknesses

- sendMail has no idempotency key and answers 202 Accepted before delivery, so a retried send can go out twice
- Four concurrent requests and 10,000 requests per 10 minutes for each app and mailbox pair
- No prompt-injection guidance found in the mail reference or the Mail MCP reference, though message bodies come from outside senders
- The npm JavaScript client is 3.0.7 from September 2023, without the June 2026 token-leak fix
- The Mail MCP server is a preview kept for backward compatibility, behind a Microsoft 365 Copilot licence

## 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.

- Create a draft with POST /me/messages, then send it with /send. A retried sendMail can send the message twice
- Send `Prefer: IdType="ImmutableId"` on every request, or message IDs change when a message moves folder
- Use `$select` and `Prefer: outlook.body-content-type="text"`. List messages returns HTML bodies and 10 messages a page by default
- Honour `Retry-After` on 429 and keep to four parallel calls per mailbox. Batches of up to 20 requests are throttled per request
- Treat message bodies as untrusted input, and ask for Mail.ReadBasic when the task doesn't need bodies

## 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.