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Mattermost

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Panel rating · 6 judges · How to read the stars

Category median

Sovereignty: 1 of 4 dimensions proven

0–5 in half steps. 5 means the rubric's top anchor is met on the evidence.

by Mattermost, Inc. · mattermost.com

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Read this page as one judge. Each weighs the same scores by what they care about.

The Skeptic

Weighted verdict

Reads for the message-history cap, the tier where SSO appears, and what "unlimited" excludes. Has seen "end-to-end encrypted" mean direct messages only, on request, with search disabled — and wants that sentence found rather than assumed.

Same scores as the panel view — this lens weights them the way this judge cares.

Scored by The Skeptic

Channels, threads & search

How this is scored

The daily surface: channel model, threading, mentions, files, and whether search can find a decision made eighteen months ago.

0 — Flat group chats with no threads; search covers recent messages only, and history is capped.

3 — Channels and direct messages with basic search, but threading is awkward or absent and file handling is a plain attachment list.

5 — Public and private channels, real threads, mentions and reactions, file sharing with previews, and full-text search across the whole history.

8 — Cross-organisation or guest channels with clear boundaries, message editing history, pinned and saved items, search with filters by channel, person and date, and a documented history limit or none at all.

10 — The archive is a working knowledge base: search that ranks well across years, threads that stay readable, channel lifecycle management (archive, rename, merge) without losing history, and export of a conversation in a form a human can read.

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The Skeptic

Channels, real threads and a documented thread API are evidenced, and at least the search cap is printed rather than hidden: core search up to three million posts on Professional, enterprise search beyond three million on Enterprise. I found no public information on pinned or saved items, mentions and reactions, or search filters by channel, person and date, and the thread-move endpoint is flagged as beta. Default behaviour retains every message including edits and deletes plus all files, so the history itself appears uncapped. 2 5 6 10

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Encryption & access control

How this is scored

What is encrypted and against whom, plus who can reach which room. Judged on documented mechanism, since "encrypted" in this category usually means the vendor holds the keys.

0 — Transport encryption only, undocumented; no role model beyond admin, guests indistinguishable from members.

3 — TLS and encryption at rest with vendor-held keys, basic roles, and guest access that mostly works.

5 — The above plus configurable roles per channel, SSO, guest accounts with scoped visibility, and a clear statement of what the vendor can read.

8 — Optional end-to-end encryption for direct messages or private rooms with the trade-offs named, device verification, session management an admin can revoke, and documented key handling.

10 — End-to-end encryption as a first-class mode — documented or open cryptography, cross-device key management that ordinary users survive, identity verification, and the vendor stating plainly what it cannot decrypt.

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The Skeptic

The sentence I hunt for exists here: the database holds messages unencrypted specifically so search and compliance reporting of history work, which means TLS in transit and disk-level encryption at rest — no end-to-end encryption claim appears on the captured pages. Single sign-on and multifactor authentication sit on Professional, granular role-based and attribute-based controls on Enterprise, so the tier map is visible. I found no public information on device verification or session management an administrator can revoke. 2 7 8

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Retention, discovery & co-determination

How this is scored

The archive as a legal object: retention policies, export for discovery, audit, and the monitoring features a works council will ask to have switched off.

0 — No retention policy, no export beyond a manual copy, no audit log, and presence or activity analytics that cannot be disabled.

3 — Manual export of some data and a global history limit, but no per-channel retention, no audit log and no admin control over analytics.

5 — Configurable retention per channel or workspace, admin export in a documented format, an audit log of administrative actions, and status or presence that a user can control.

8 — Legal-hold and eDiscovery export including edits and deletions, retention executed per policy and evidenced, full admin audit trail, and activity analytics switchable off organisation-wide.

10 — Built to pass a works agreement and a subpoena on the same day: granular retention with documented deletion, discovery export a lawyer can use, complete audit, and no individual-level productivity scoring anywhere in the product.

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The Skeptic

The discovery machinery is unusually concrete: compliance exports in CSV, Actiance XML, Global Relay EML and Proofpoint formats, edits and deletions tracked by message ID, channel member history included, past history exportable by command line, and every query and download logged in an audit history — with Playbooks and Boards explicitly excluded, which I respect being told. Legal hold and data retention policy appear as feature names on Enterprise without documented mechanism, and the audit trail I can see covers compliance queries rather than all administrative actions. I found no public information on activity analytics being switchable off organisation-wide. 2 4 9 10

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Deployment & data custody

How this is scored

Whether the customer can hold their own archive: self-hosting, private cloud, open source, federation, and what an exit actually looks like.

0 — Cloud-only, proprietary, with export limited to a partial archive.

3 — Cloud-only, but with a documented full export in an open-ish format.

5 — A private-cloud or dedicated-instance option, or a self-hosted edition that lags the cloud significantly; full export documented.

8 — A genuine self-hosted edition close to feature parity, or open-source core with a documented upgrade path, plus complete export including files and metadata.

10 — Custody is the customer's: open-source or source-available server, self-hosting supported as a first-class deployment, open protocol or federation, and a migration path in and out that the vendor documents rather than resists.

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The Skeptic

Self-hosting is documented as a first-class path: Kubernetes, Linux and container methods install the same server, an air-gapped runbook with registry mirroring is published, FIPS-compliant STIG-hardened images exist, and the privacy policy states the customer controls processing of end-user data on self-hosted products. Federation via Matrix protocol interoperability is listed at Enterprise tier. The captured pages do not state a licence or source-availability model for the server, so I score the deployment paths rather than assume an open-source core. 2 4 11 12

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Integrations & extensibility

How this is scored

Bots, webhooks, app framework, identity — whether the chat becomes the place work is noticed, and whether that is buildable without a partner agreement.

0 — No API, no webhooks, no bots.

3 — Incoming webhooks and a handful of native integrations; no bot framework, no documented limits.

5 — Documented REST API, incoming and outgoing webhooks, slash commands, a bot account model, and SSO.

8 — A proper app framework with interactive components, event subscriptions with retries, SCIM provisioning, documented rate limits and a sandbox.

10 — A platform: versioned API with a deprecation policy, an app directory or plugin system with permissions a customer can audit, and integrations the vendor maintains rather than lists.

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The Skeptic

A versioned REST API with bearer authentication, incoming and outgoing webhooks with Slack-compatible payloads, interactive dialogs and structured interactive blocks, plus single sign-on — a solid middle of this scale. I found no public information on slash commands, SCIM provisioning, documented rate limits, an app directory or a sandbox. Bot posts are acknowledged in compliance export contents, but no bot account model is documented on the captured pages. 2 6 13 14

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European sovereignty

How this is scored

Where the archive and its metadata live, who the contracting entity is, which subprocessors touch it. Independently sourced by the sovereignty pipeline; scored here as this buyer weighs it.

0 — Non-EU vendor and contracting entity, hosting unstated or non-EU, subprocessors unnamed.

3 — EU data residency offered for message content while metadata, search indexes or support tooling remain non-EU, or the contracting entity sits outside the EU.

5 — EU hosting as standard and an EU contracting entity, but parts of the chain — notifications, AI features, analytics — are non-EU without an explained safeguard.

8 — EU hosting on named infrastructure, EU contracting entity, full subprocessor list published, any non-EU processing named with its legal basis.

10 — Sovereign end to end and evidenced: vendor, entity, hosting and every subprocessor European, certification published, and a self-hosted option that removes the question.

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The Skeptic

The contracting entity is Mattermost, Inc. in the United States, transfers to the USA are disclosed, and reliance is on the EU-U.S. Data Privacy Framework and Standard Contractual Clauses; the captured pages give no hosting location and no published subprocessor list for the vendor-managed cloud, while Azure and AWS appear as cloud options for US-headquartered providers. What lifts this off the floor is documented self-hosting where the customer controls the data and telemetry can be opted out — custody can move to the customer, but the vendor chain remains American and its footprint remains unstated. 2 3 4

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Pricing transparency not rated — the vendor publishes no price

How this is scored

Whether a buyer can compute the annual invoice for their headcount — including the retention, compliance and guest features they actually need — from public pages alone.

0 — No public prices at all; every tier is a sales conversation.

3 — A per-user headline exists, but the tier where retention control, SSO or compliance export begins is unstated.

5 — Per-user prices public with billing period stated, but at least one commonly needed capability (unlimited history, SSO, eDiscovery) sits in an unpriced enterprise tier.

8 — Every tier priced publicly with per-user maths, history and storage limits, feature boundaries, minimum term and VAT treatment stated; self-hosted licensing priced too where offered.

10 — Complete price computability: annual invoice derivable for a given headcount and deployment choice, including guest users, storage and any per-instance licence.

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The Skeptic

Every tier routes to sales — Professional says Contact Sales, Enterprise says Get Pricing, Enterprise Advanced says Request Quote — and no per-user figure appears anywhere on the captured pricing pages. Credit for labelled tier boundaries: single sign-on at Professional, compliance export and retention policy from Enterprise, Professional support capped at 250 users, plus a free limited-use evaluation edition. No annual invoice is computable from the public pages, whatever the headcount. 2

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European sovereignty — proven facts

1 of 4 dimensions proven

Built only from facts shown on the vendor's own pages. A dimension we could not prove is left open, not scored as zero.

Ownership Not determined — uncited Report an error
Data residency Not determined — uncited Report an error
Subprocessors US CLOUD Act reach ⚠ unverified 0/2 pts 3 Report an error

Where this could be wrong

What we left out

A claim that does not survive our checks costs us the claim, not the page. This is what was taken off this one.

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Sources (14)

The pages every claim on this page was read from — each one checked, dated, and kept verifiable.

  1. 1 Vendor homepage mattermost.com Checked 15 Sep 2026 Details →
  2. 2 Pricing mattermost.com Checked 15 Sep 2026 Details →
  3. 3 Security page mattermost.com Checked 15 Sep 2026 Details →
  4. 4 Privacy policy mattermost.com Checked 15 Sep 2026 Details →
  5. 5 Channels, threads & search — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  6. 6 Channels, threads & search — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  7. 7 Encryption & access control — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  8. 8 Encryption & access control — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  9. 9 Retention, discovery & co-determination — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  10. 10 Retention, discovery & co-determination — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  11. 11 Deployment & data custody — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  12. 12 Deployment & data custody — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  13. 13 Integrations & extensibility — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →
  14. 14 Integrations & extensibility — found from sitemap docs.mattermost.com Checked 1 Oct 2026 Details →