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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 Security Officer

Weighted verdict

Assumes the archive will one day be read by someone it was not meant for. Wants end-to-end encryption that ordinary users survive, device verification, sessions an admin can revoke, and a plain statement of what the vendor cannot decrypt.

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

Scored by The Security Officer

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 Security Officer

Channels, real threaded discussions, file previews and search up to three million posts are documented on the plan pages, the API exposes threads with collapsed-thread views, and a beta call can move a thread to another channel. By default every deployment retains all messages, edits and deletions included, so the history itself is uncapped. We found no public information on pinned and saved items, on end-user search filters by channel, person or date, or on channel archiving and renaming that preserves history. 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 Security Officer

Transport is TLS throughout, encryption at rest is infrastructure-level — LUKS, BitLocker, TDE, S3-managed keys — and granular roles, SSO, MFA and attribute-based channel access are all documented. The plain statement I prize is there, in an unwelcome direction: the deployment guide says encryption within the database is not offered, precisely so end-user search and compliance reporting can work, which tells me the server and whoever operates it reads everything. We found no public information on end-to-end encryption, device verification, or sessions an administrator can revoke. 2 4 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 Security Officer

Legal hold, eDiscovery automation and exports in CSV, Actiance XML, Global Relay EML and Proofpoint formats are documented, carrying edits, deletions, file uploads and channel member history, with messages trackable by identifier across batches and query and download actions logged in an audit history. Retention is retain-everything by default with plan-dependent customisation, jobs report success with counts, and past history can be exported by timestamp from the command line. Two honest gaps: Playbooks and Boards content sits outside the compliance export, and we found no public information on per-channel retention granularity, a full administrative audit trail, or switching off activity analytics 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 Security Officer

Custody is genuinely on the table: three deployment methods install the same server, high availability is self-managed, and an air-gap runbook with bill of materials and registry mirroring covers every edition from Team Edition upward, with FIPS-compliant, STIG-hardened images published. Export covers past history, files and member history into my own filestore, and Matrix protocol interoperability is named for federation. The door itself is the remaining question: we found no public information on the source licence terms behind the Team Edition or a documented migration path for bringing a legacy archive in. 2 9 11 12 13

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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 Security Officer

A documented REST API with bearer authentication and per-channel permission checks, incoming and outgoing webhooks on every plan, Slack-format compatibility, interactive Blocks with buttons and menus, interactive dialogs and administrator-enforced webhook channel locking make a real integration surface, and a Model Context Protocol connector is named at the Enterprise tier. The admin control over which channels a webhook may post to is exactly the kind of boundary I want to see. We found no public information on SCIM provisioning, event subscriptions with retries, documented rate limits, a sandbox, or an app directory with permissions a customer can audit. 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 Security Officer

The contracting entity is Mattermost, Inc. of Palo Alto; we found no public information confirming EU data residency, and the captured security page names Azure and AWS as cloud options for US-headquartered providers without listing the subprocessors of the vendor-managed cloud. Transfers to the United States are disclosed with Data Privacy Framework certification, Standard Contractual Clauses and a TRUSTe referral path, and self-hosting with customer-controlled processing is the real mitigation — but even there, hosted push notifications can carry usernames, channel names and message preview snippets to the vendor unless the customer keeps that service off. For a European buyer this is a US chain with an escape hatch, not a sovereign one. 3 4 11 12

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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 Security Officer

The captured pricing pages route every named plan to a human — Professional says "Contact Sales", Enterprise says "Get Pricing", Enterprise Advanced says "Request Quote" — and no per-user figure, billing period or VAT treatment appears anywhere. A free limited-use edition of Enterprise Advanced exists for technical evaluation, while compliance monitoring sits in the quote-only tiers. I cannot compute an annual invoice for any headcount from these pages. 2 10 12

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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 →