Microsoft Teams vs Mattermost: when self-hosted chat is the better fit
Teams fits organizations that are deeply tied to Microsoft 365 and Entra ID, while Mattermost fits organizations that need chat hosted in their own infrastructure under an open-source license. The question usually starts with a renewal, a licensing change, a data residency rule or a lock-in concern, and it is worth asking whether Teams chat should leave the Microsoft 365 suite at all. Since April 1, 2024, Microsoft sells Microsoft 365 and Office 365 suites without Teams outside the EEA and Switzerland, and existing suites that include Teams are no longer sold to new subscribers worldwide, so the licensing question is now a live decision for many buyers.
The decision turns on five things: integration needs, data control, identity requirements, edition needs and operating capacity. Ask which Microsoft 365 workflows depend on Teams, such as channel files in SharePoint, calendar-linked meetings in Outlook or compliance tooling already configured in the tenant. Then check identity. Mattermost offers single sign-on through SAML, OIDC and OAuth and AD/LDAP user sync, but in the Mattermost pricing page these features sit in the paid Professional plan and above, not in the free Team Edition. High availability, which needs redundant application servers, database servers and load balancers, is limited to Enterprise and Enterprise Advanced. Confirm these against the current pricing page before you size the project.
Operating capacity is the factor most often underestimated. A Mattermost deployment runs on Linux with PostgreSQL, and a high availability cluster needs shared file storage on Amazon S3, an S3-compatible service or NAS mounted on every node, because local file storage will not work correctly and risks corrupting files. Your team will also need to apply monthly server releases and plan around support windows, so ask which version lines your staff can track. If you lack that capacity in-house, a fixed-scope implementation and a support retainer from DeployOpen can cover build, hardening, backup and upgrades inside your own environment, with the scope agreed in writing before work starts.
Which option fits which scenario
This table matches common Teams replacement scenarios to the option that fits best and the reason why. Read each row against your own constraints, such as Microsoft 365 dependencies, residency rules, team size and the identity tier you need. The main takeaway is that Mattermost fits best when chat must be self-hosted, but SSO and high availability sit in paid tiers.
| Scenario | Better fit | Reason |
|---|---|---|
| Heavy Microsoft 365 and Teams-embedded workflows | Stay in Teams or keep Teams for meetings | Mattermost has no built-in Office, SharePoint or Teams app integration, so embedded workflows need rebuilding through its integrations. |
| Data residency or sovereignty requirement | Mattermost (self-hosted) | Messages and files stay on servers you control, but confirm your hosting location and backup regions with your own counsel. |
| Small team wanting a free self-hosted start | Mattermost Team Edition | Team Edition is free and open source, aimed at teams under 250 users that do not need single sign-on. |
| Regulated organization needing SSO and high availability | Mattermost Enterprise tier | SSO and AD/LDAP sync start at Professional, while high availability is available only on Enterprise and Enterprise Advanced plans. |
| Dropping the Teams license but keeping Microsoft 365 | Mattermost with Entra ID SSO | Entra ID sign-on needs the Professional tier or higher, so confirm the identity tier before you drop Teams. |
| Air-gapped or disconnected network | Mattermost Enterprise Advanced | Air-gapped deployment is listed in Enterprise Advanced only, so check this against your network requirement. |
| Migrating an existing Teams history archive | Mattermost with a custom import | Teams history moves through Graph export and a bulk import, which requires admin-approved permissions and active Teams licenses on exported users. |
What an organization gives up and gains when chat leaves Microsoft 365
Moving chat out of Microsoft 365 means giving up the tight coupling between Teams and the rest of the suite. Teams chat sits inside Entra ID sign-in, Outlook calendars and mail, and SharePoint and OneDrive file storage, and meetings started from a channel carry their context with them. When a Mattermost server replaces that chat, none of those links exist unless someone builds them. Mattermost has its own user, team and channel model, so the Teams team-to-channel structure has to be remapped, and the file tabs, Outlook notifications and calendar-based meeting links need separate integrations or replacement workflows. Ask which of these links your staff use daily, because the users who rely on them will feel the loss first.
The gains are concrete and sit in four areas. You choose where messages are stored and on which infrastructure, which matters most when data control rules restrict where chat content may live. The Mattermost Team Edition is free, open source and self-hosted, and its server is MIT-licensed as compiled by Mattermost, so licensing terms do not determine the architecture. You also choose the hosting model, from a single Linux binary on PostgreSQL to a high availability cluster, and you are not exposed to the suite's pricing or packaging changes, such as the April 1, 2024 unbundling of Teams from Microsoft 365 suites. These gains weigh most when licensing pressure or lock-in is the driver. Confirm the license that applies to your build, since Mattermost source code is licensed under AGPL v3.0 with a commercial option.
Plan the cost side before the gains. Mattermost SSO (SAML, OIDC and OAuth) and AD/LDAP sync sit in the paid Professional plan, and high availability requires Enterprise, so an organization that depends on Entra ID sign-in and directory sync should price that edition before committing. High availability also needs shared file storage on Amazon S3, an S3-compatible service or NAS, because local storage risks file corruption. Ask your Mattermost partner or sales contact for a quote tied to your seat count and required features, and ask your own platform team who will operate the server, the database and the storage. Those staffing costs recur every year, and they are the largest difference from a Teams subscription.
Where the data lives and who controls it
Chat history is often the most sensitive data a team generates, and the question is who holds the keys to it. The cards below compare where Teams stores messages with a self-hosted Mattermost deployment, and which Mattermost edition gives you the identity, retention and audit controls a regulated organization usually needs.
Where Teams content sits
Teams chat, channel messages and files are stored in Microsoft 365 service regions and managed by Microsoft under its own operations. Your control is limited to the tenant settings, retention policies and data residency options Microsoft exposes. Ask your Microsoft account team which regions your tenant uses and which controls you can configure, then document that answer for your risk register.
Self-hosted Mattermost placement
A self-hosted Mattermost server runs as a single Linux binary backed by PostgreSQL, so you choose the data center, cloud account or air-gapped network where messages and attachments live. You also decide the backup targets and who holds administrative access. Confirm the file storage backend and database location in your own architecture review before any user data is imported.
Edition sets the control set
Team Edition is free, open source and aimed at teams under 250 users without single sign-on. Professional, Enterprise and Enterprise Advanced add the identity, clustering and disconnected deployment features that regulated buyers typically need. Map each control your auditors expect to a specific edition on the pricing page, because features that are absent in a lower tier cannot be added by configuration.
Identity through SAML, OIDC or LDAP
Teams relies on Entra ID for sign-in and conditional access. In Mattermost, single sign-on through SAML, OIDC or OAuth is included from the Professional plan, and AD/LDAP user sync is available at the same tier. Confirm that joiner, mover and leaver events in your directory will deprovision Mattermost accounts, since a disabled user who keeps an active chat session is a common gap.
Retention and audit logging
Teams retention is set through Microsoft Purview policies, and export depends on the Teams Export APIs and the licenses behind them. With Mattermost, retention and compliance export are tied to paid tiers, and the Entry tier caps channel history at 10,000 messages. Decide your retention periods and audit log destinations first, then check which Mattermost plan provides the compliance export you need.
Evidence is yours to assemble
DeployOpen plans, configures and documents the Mattermost controls and prepares the evidence your assessor will ask for, such as configuration exports, access reviews and backup test records. DeployOpen does not issue audit reports, attestations or certifications, and independent auditors or certification bodies make those determinations. Ask each candidate partner to state this boundary in the written scope.
Mattermost licensing and editions compared with Teams licensing
Mattermost licensing has three layers, and legal review should check each one separately. The compiled server binaries are licensed under the MIT license, which is permissive and places few conditions on use. The source code for custom builds is licensed under AGPL v3.0, and Mattermost, Inc. offers a commercial license as an alternative. If your team modifies that source and makes the modified server available to users over a network, the AGPL's source-sharing obligations become the first question for counsel. Admin tools and configuration files fall under Apache 2.0. Ask counsel to confirm which artifact you will deploy, whether you will build from source, and whether the commercial license is needed.
The edition ladder determines which features you pay for. Team Edition is free, open source and self-hosted, aimed at teams under 250 users that do not need single sign-on. Entry is the free tier of the commercial build and caps channel message history at 10,000 messages, with no compliance features or high availability. Professional adds SSO through SAML, OIDC and OAuth, plus AD/LDAP user sync. Enterprise adds high availability clustering and FIPS 140-3 compliance, and Enterprise Advanced adds air-gapped deployment. Confirm the current feature matrix in the editions documentation before you choose a tier, because clustering also has infrastructure requirements that cost money of their own.
Teams licensing is a different kind of decision because it moves with the Microsoft 365 suite. Since April 1, 2024, Microsoft sells Microsoft 365 and Office 365 suites without Teams outside the EEA and Switzerland, offers a standalone Teams offering, and no longer sells suites that include Teams to new subscribers worldwide. If you drop Teams from the suite, the chat cost becomes a separate line item that you can compare directly with a Mattermost subscription. Mattermost sells Professional, Enterprise and Enterprise Advanced as prepaid annual subscriptions based on seat licenses, and its pricing page lists no public prices. Get the edition, seat count, seat definition, term, renewal and support terms in writing before you compare totals.
Cost components: Teams licenses against self-hosted Mattermost
Teams cost sits mostly in per-user Microsoft 365 licensing that recurs every month or year, while self-hosted Mattermost splits into a software subscription, infrastructure, and the people who run it. The cards below show which costs are one-time, which recur, and what to ask for before comparing totals.
Teams per-user licensing
Teams chat is included in Microsoft 365 suites that carry it, so the cost is usually the suite license, not a separate Teams line. Since April 1, 2024, Microsoft sells suites without Teams outside the EEA and Switzerland, and existing suites with Teams are no longer sold to new subscribers worldwide. Confirm with your Microsoft partner which SKU you hold, because dropping Teams may change the per-user price and the other apps bundled with it.
Mattermost subscription by seat
Mattermost Team Edition is free, but SSO and AD/LDAP sync start at the Professional plan, and clustering and FIPS 140-3 compliance start at Enterprise. Paid plans are prepaid annual subscriptions based on seat licenses, and the pricing page lists no public prices, so ask sales for a quote that states the seat count, plan, term and support level. Seat counts for contractors and guests should be confirmed in writing.
Application servers and load balancers
A high availability cluster needs redundant application servers and redundant load balancers, and that is available only on Enterprise and Enterprise Advanced. Each node is an ongoing compute cost, and you pay for the cloud or hardware in both the primary and standby sites. Ask your team to size the cluster for peak concurrency, not average use, because undersized nodes are the most common reason clusters fail under load.
PostgreSQL and read replicas
Mattermost runs on PostgreSQL, and high availability requires redundant database servers. Read replicas and search replicas spread read traffic, while writes still go to the primary. Managed PostgreSQL adds a recurring service fee but removes patching and failover work, while self-managed PostgreSQL moves that cost into staff time. Confirm backup retention and restore testing as line items in the plan.
Shared file storage on S3 or NAS
A high availability cluster must share file storage through Amazon S3, an S3-compatible service, or a NAS mounted on each node. Local file storage will not work correctly and risks corrupting files. Object storage usually bills by volume stored and requests, so storage growth from attachments is the cost driver to model. NAS hardware is a one-time purchase with maintenance and replacement costs that recur over its life.
Staff time, support and upgrades
Self-hosting moves the cost of administration, patching and upgrades onto your staff or an implementation partner. Mattermost publishes server releases monthly, and the Extended Support Release track gives longer support windows, so the plan should name who applies each release and who tests it. Support contracts from the vendor and retainers from a service provider are recurring costs to price separately from one-time migration work.
How a move from Teams to Mattermost is structured
The sequence runs from identity and hosting decisions through a tested data extraction and import to a supervised cutover, and each phase ends with a check the organization can verify before the next one starts. Teams chat history is the hardest part, so it is handled as its own phase rather than folded into the build.
Scope channels, identity and retention rules
The organization, with its Microsoft 365 administrators and compliance owners, decides which Teams teams, private channels and chat histories move, which stay in Teams for a defined period, and which users need Mattermost accounts. It also sets how Entra ID sign-in will map to Mattermost users, since single sign-on with SAML or OIDC and AD/LDAP sync are licensed features on Mattermost paid plans. Confirm the edition and features against the Mattermost pricing page before design work starts. The output is a signed scope document listing teams, users, identity method and retention requirements.
Build hosting and the high availability design
The platform team deploys Mattermost on the organization's own infrastructure with PostgreSQL as the database and a shared file store reachable from every node. Mattermost's high availability setup needs redundant application servers, database servers and load balancers, and it is available only on the Enterprise and Enterprise Advanced plans. Local file system storage will not work correctly in a cluster and risks corrupting files, so the team must confirm Amazon S3, an S3-compatible service or NAS is available before building. The check is a test instance that stores and retrieves an uploaded file from every node.
Extract Teams history through Microsoft Graph
A Microsoft 365 administrator approves the application permissions that the Teams Export APIs in Microsoft Graph require, and each user whose content is exported must hold an active Teams license at the time of export. The export returns 1:1, group, meeting and channel messages, plus meeting recording and transcript links, so the team should decide in advance which of those artifacts become Mattermost content and which remain as links. The check is a complete export for a small pilot set of teams, with message counts compared against what users see in Teams.
Convert exports to Mattermost bulk import format
Engineers transform the Graph output into Mattermost's bulk import format and load it with mmctl, mapping Teams teams and channels to Mattermost teams and channels, and mapping Teams users to the accounts created in the identity phase. The Teams export is a separate path from the Slack migration tooling, which converts a Slack export with mmetl, so the converter is custom work and needs its own test cases for threads, edited messages, attachments and deleted users. The check is a re-import into a staging server with a diff report showing that message counts, threads and attachments match the source.
Run a supervised pilot with a small group
A limited set of teams uses the imported Mattermost workspace for normal work for a period agreed in the project plan, with a named owner collecting issues on sign-in, notifications, file access, mobile use and search. Integrations from Teams, bots, custom emoji and any Teams-only apps will not come across, so the pilot should list every workflow that depended on them and assign replacements. The check is a signed pilot report listing defects, workarounds and acceptance by the business owners of each pilot team.
Cut over users and retire Teams chat
The team sets a cutover date, runs a final incremental export and import, switches users to Mattermost, and communicates the new channels and links to Teams for staff. Teams chat is set to read-only or retired according to the retention decision made in the scoping phase, and any Microsoft 365 licensing change is coordinated with procurement. The check is a rollback plan tested in staging and a checklist showing every team has an active owner and every user can sign in.
Preserve retention and operate the platform
After cutover, the operations team keeps the Teams export evidence and the import logs under the retention rules set in scoping, so that records remain available for legal or audit requests after Teams content is removed. The team also owns backups of the PostgreSQL database and the file store, the Mattermost upgrade schedule, and monthly server releases as published by Mattermost. Ask the vendor for the support window of the version you deploy. The check is a documented restore test and a retention schedule approved by compliance.
Questions buyers ask before choosing Mattermost over Teams
What does it cost to run a self-hosted Mattermost deployment?
The software itself has no license fee on the Team Edition, so the recurring cost is the infrastructure, the people who operate it and any paid Mattermost subscription you add. Infrastructure covers application servers, PostgreSQL, file storage and backups, and it grows with user count, message volume and file retention. Staff time covers patching, monitoring, backup testing and user support. Paid Professional, Enterprise and Enterprise Advanced plans are prepaid annual subscriptions priced by seat licenses, and Mattermost's pricing page lists no public prices, so ask Mattermost for a seat quote. Ask DeployOpen for a written scope that separates one-time setup from recurring operations.
How long does a Teams to Mattermost migration take?
The timeline depends on scope, and it is set in writing before work starts. The main drivers are the number of teams, channels and users, how much history you keep, whether you move files and meeting recordings, the identity integration, and how many integrations must be rebuilt. Chat history can be pulled through the Microsoft Graph Teams Export APIs, which need admin-approved permissions and active Teams licenses on the exported users, then loaded through Mattermost's bulk import format. Plan a parallel-run period and a cutover window, and confirm both with your DeployOpen scope.
Can our internal team run Mattermost on its own?
Yes, many internal teams run it, but it needs people with Linux, PostgreSQL, reverse proxy and container or server operations skills, plus someone who owns upgrades. Mattermost publishes a new server version in binary form on the 16th of each month, and Mattermost v11.7 is an Extended Support Release with support ending 2027-05-15, so an upgrade calendar matters. High availability and clustering need operations skill with shared storage and database replicas. Check whether your team has these skills in-house, and consider a DeployOpen retainer for upgrades and continuous support if they do not.
Can Mattermost keep Entra ID sign-on, and which edition includes SSO?
Mattermost can use single sign-on through SAML, OIDC and OAuth, and its pricing page places SSO and AD/LDAP user sync in the Professional plan and above. Team Edition is aimed at teams under 250 users that do not need single sign-on, so Entra ID sign-on requires a paid plan. Confirm the exact SAML or OIDC configuration with Mattermost's SAML documentation and test group mapping, deprovisioning and session lifetime in a pilot before cutover. Ask your identity team to confirm the claims and attributes they will release.
Do Slack-style imports or the Teams Export APIs carry over meetings, recordings and files?
Mattermost's Slack migration path, which converts a Slack export with mmetl, moves users, channels, direct messages, threads and attachments, but it does not move integrations, custom emoji images, user groups or Slack Connect channels. Teams has no equivalent Mattermost importer, so chat and channel history must be extracted through the Microsoft Graph Teams Export APIs, which return 1:1, group, meeting and channel messages plus meeting recording and transcript links. Those links point to content that stays in Microsoft's storage, so you must download and store recordings separately. Confirm each content type in your scope, because some items may need a custom conversion step.
What does high availability require in Mattermost?
High availability is available only on the Enterprise and Enterprise Advanced plans. It consists of redundant application servers, redundant database servers and redundant load balancers. A cluster needs shared file storage on Amazon S3, an S3-compatible service or NAS mounted on each node, because local file system storage will not work correctly and risks corrupting files. Read replicas and search replicas can scale concurrent users and reduce latency, with writes going to the primary database. Confirm the storage and network design against Mattermost's deployment planning guide before committing to a topology.
What does our staff need to provide for the engagement?
Expect to provide named owners for identity, network, storage, backup and the Teams tenant, plus decisions on which channels, users and retention periods move. Your identity team confirms Entra ID application registration and attribute release. Your Microsoft 365 administrator approves the Graph permissions and confirms Teams licenses for the export. Your security team reviews data classification, retention and logging, and your operations team accepts the runbook. Staff time is a real cost you should price into the internal side of the plan, and DeployOpen will list these responsibilities in the written scope.
How DeployOpen helps evaluate, implement and migrate
DeployOpen plans, implements, integrates, hardens, backs up and documents a self-hosted Mattermost deployment inside your own infrastructure, whether that is your cloud accounts, your data center or an air-gapped network. For a Teams replacement, the work usually starts with decisions that a chat product alone does not answer: which Mattermost edition fits your user count and identity requirements, where the file storage and PostgreSQL database will live, how single sign-on will be wired to your identity provider, and whether you need a high availability cluster at all. We can document each decision in a written design so that your security, compliance and platform teams review the same facts before any build starts.
Migration scoping is a separate step and deserves its own written scope. Pulling Teams chat and channel history depends on Microsoft Graph Teams Export APIs, admin-approved application permissions and active Teams licenses on the users being exported, so the first thing to confirm is whether your tenant can grant those permissions and whether the history you need still exists. Integrations, custom emoji images, user groups and any Teams apps will not carry over, so we would inventory them with your teams and agree in writing what is rebuilt, what is retired and who signs off. Most engagements are fixed-scope, with scope, deliverables and timelines agreed in writing before work starts. Ongoing upgrades, backups testing and support can follow under a retainer, and separate security testing of the deployment can be scoped alongside it.
DeployOpen prepares systems, configurations and evidence that your compliance assessment can use, but we do not issue audit reports, attestations or certifications. Independent auditors and certification bodies perform those assessments, so confirm early which of your obligations they will examine and which evidence they expect from the chat platform. Ask for a quote built from the written scope, and check that it names the environment, the number of users, the identity integration, the migration boundary and the support period. DeployOpen does not publish a price list.
