Skype for Business Server or Mattermost: which fits an on-premises chat estate
Mattermost can replace the chat and presence role of Skype for Business Server for teams whose needs centre on persistent channels, direct messages and file sharing, and it runs entirely in your own datacenter as a single Linux binary backed by PostgreSQL. It does not replace the telephony, room system and conferencing functions that many Skype estates also depend on, so those need a separate plan before any decommissioning decision. Keep Skype for Business Server where existing Microsoft dependencies, Enterprise Voice trunks or room devices are tightly bound to it and changing them would cost more than the chat function is worth.
Mattermost fits best when chat is the primary workload and data control is the driver. Team Edition is free and open source, but it is aimed at teams under 250 users that do not need single sign-on, so most on-premises estates will need a paid edition. Per the Mattermost pricing page, SSO (SAML, OIDC, OAuth) and AD/LDAP user sync start at the Professional plan, while high availability clustering starts at Enterprise. Ask the vendor to confirm which plan covers your login method, directory sync and redundancy requirements, because those features determine the price more than user count does. Note that high availability needs shared file storage such as NAS or an S3-compatible store on every node, which is an infrastructure cost that Skype's own design did not carry in the same form.
The decision turns on four questions: whether you need SSO and AD/LDAP sync from day one, how much telephony and meeting scope must move with chat, whether you need clustering for availability, and which operating skills your team has. Map each Skype feature you use today, including presence, persistent chat rooms and federation, against what Mattermost provides and what must come from a separate video or telephony service. Confirm the Skype functions you depend on with your own usage reports before scoping, because an estate that uses only instant messaging and presence is very different from one that runs Enterprise Voice and room systems on the same servers.
Which scenarios favor Skype for Business Server and which favor Mattermost
This table compares common on-premises scenarios and names the platform that usually fits better, with the conditions that change the answer. Read each row against your own telephony, identity and availability requirements. The main takeaway is that Mattermost covers chat and presence well, while voice, room systems and some enterprise controls need components from elsewhere.
| Scenario | Better fit | Reason and conditions |
|---|---|---|
| Chat only, with no voice or room systems | Mattermost | Mattermost covers channels, direct messages and file sharing without a telephony stack. Confirm that presence and mobile clients meet your users' needs before cutover. |
| Telephony and PSTN dependence | Skype for Business Server | Enterprise Voice, call routing and PSTN trunks are not part of Mattermost. If you rely on them, plan a separate telephony platform and confirm it before retiring SfB. |
| Active Directory login with no SSO requirement | Mattermost Team Edition | Team Edition is free and self-hosted for teams under 250 users without single sign-on. Larger groups or stricter login policies will need a paid edition. |
| SSO and AD/LDAP sync required | Mattermost Professional or higher | SSO (SAML, OIDC, OAuth) and AD/LDAP user sync are included from the Professional plan according to the Mattermost pricing page. Ask the vendor to confirm current plan contents. |
| High availability requirement | Mattermost Enterprise or Skype for Business Server, depending on design | Mattermost high availability is available only on Enterprise and Enterprise Advanced plans and needs shared file storage on each node. Confirm that your storage and database redundancy match your uptime targets. |
| Air-gapped network | Mattermost Enterprise Advanced or Skype for Business Server | Air-gapped deployment is listed for Enterprise Advanced. Confirm update and licensing paths with the vendor before committing, since disconnected networks change how patches arrive. |
| Staff who already run Windows and SQL Server operations | Skype for Business Server | Existing Windows and SQL Server skills lower the operational learning curve for SfB. Mattermost runs as a Linux binary with PostgreSQL, so budget for Linux and database skills if they are missing. |
What Mattermost covers from Skype for Business chat, and what it does not
Mattermost provides one-to-one and group direct messages, online status for users, and notifications across desktop, web and mobile clients. This covers the day-to-day instant messaging that most Skype for Business users rely on. Presence in Mattermost is a chat-status signal, not a telephony presence feed, so it does not reflect calls handled by a PBX or a SIP trunk unless you connect those systems yourself.
- Direct messages: One-to-one and small group conversations are available in the client, with status indicators for users.
- Status sources: Status reflects Mattermost activity, so calendar or phone-state presence needs an integration you build or source separately.
- Federation: Mattermost does not federate with other organizations' servers the way Skype for Business did with partners, so external contacts need guest accounts or another channel.
- Mobile clients: Confirm that your users' devices and push notification path work inside your network before cutover.
The gap matters most where users depend on presence to route calls. Confirm the status behavior you need with a test group of users in your own environment.
Skype for Business group chats were ad hoc and short-lived, while Mattermost organizes conversation into teams and channels that persist, can be public or private, and keep searchable history. Moving persistent chat rooms to channels is usually a change in how teams organize work, not only a change in software. Retention and history depend on how you configure the server and your edition, so confirm them before you promise users continuity.
- Channels: Public and private channels replace persistent chat rooms and group threads.
- Threads: Replies can be grouped within a channel to keep discussions readable.
- Edition limits: The free Team Edition is aimed at teams under 250 users without single sign-on, and the commercial free tier caps channel message history at 10,000 messages.
- Guest access: External participants need accounts set up by an administrator.
The edition and history limits matter most for regulated teams that must keep conversations for a set period. Check your retention requirements against the edition you choose.
Mattermost supports file attachments inside channels and direct messages, so files shared in chat stay with the conversation. Where files need co-authoring or versioned document storage, Skype for Business relied on SharePoint or file shares, and those systems remain separate. Plan file storage deliberately, because the storage backend also determines whether a high availability cluster works correctly.
- Attachments: Files shared in chat are stored by the server and linked to the conversation.
- Document co-authoring: Office co-authoring and document libraries are outside Mattermost and need your existing file platform.
- Clustered storage: A high availability cluster needs shared storage such as Amazon S3, an S3-compatible service or NAS mounted on each node, because local file system storage risks corrupting files.
- Migration: Attachments move during a Slack import, but file types, sizes and storage limits should be checked against your own policy.
The storage design matters most when you run clustered servers or handle large files. Confirm the shared storage option and file size limits with your platform team before you build.
Enterprise voice, meeting audio and video, and room systems are not part of Mattermost's chat function. Skype for Business often carried PSTN calling, Enterprise Voice, dial-in conferencing and conference room devices, and those capabilities must be provided by other systems. Do not assume a chat replacement covers them. Mattermost integrates with other tools through its integration model, but you should confirm each integration against your own telephony and conferencing environment rather than rely on a general statement.
- Enterprise voice: PBX, SIP trunking and PSTN calling need a separate telephony platform.
- Meeting audio and video: Conferencing needs a dedicated service such as an open-source conferencing platform run on your own servers.
- Room systems: Conference room devices and their scheduling need their own vendor or open-source stack.
- Calendar and dial-in: Meeting invitations and dial-in details need a deliberate design with your calendar system.
This is where the gap matters most. If your Skype for Business estate handled calls or meetings for daily work, plan those services separately and confirm each one with your telephony and facilities teams before decommissioning anything.
Capabilities compared: Skype for Business Server and Mattermost
This table compares the capabilities a Skype for Business estate relies on with what Mattermost offers in each edition. Mattermost edition facts come from the supplied documentation, while Skype for Business Server behavior should be confirmed against your own deployment and Microsoft's current documentation. Read the rows marked for confirmation as the items to verify before you commit to a design.
| Capability | Skype for Business Server | Mattermost |
|---|---|---|
| Presence and instant messaging | Presence and IM are core functions of the front end servers, with clients on Windows and other platforms. Confirm the exact client support for your versions. | Direct messages and presence status are part of the server. Confirm presence behavior with your clients and mobile apps. |
| Group chat and channels | Persistent chat rooms and group conversations on the front end pool. Confirm room limits and policy settings with your administrator. | Public, private and direct channels with threads. Channels replace persistent chat rooms in a migration. |
| Persistent chat history | Persistent chat history depends on the chat server configuration and retention policy. Confirm your retention settings. | Channel message history is available in paid editions without the Entry cap of 10,000 messages. Confirm retention settings for your edition. |
| File sharing | File transfer and sharing in conversations, with limits set by server policy. Confirm size limits in your deployment. | File attachments in channels, stored on the server or on shared storage. High availability needs S3 or NAS on each node. |
| Identity integration | Built on Active Directory with Windows authentication. Confirm your domain and trust design. | Connects to Active Directory through AD/LDAP sync, a paid feature from the Professional plan. |
| Single sign-on | Windows integrated authentication and federation options. Confirm the setup for your identity provider. | SSO with SAML, OIDC and OAuth from the Professional plan, per the Mattermost pricing page. |
| High availability | Pools and Enterprise Edition topology across front ends and back ends. Confirm the design your Microsoft documentation requires. | Clustering with redundant application servers, databases and load balancers, only in Enterprise and Enterprise Advanced. |
| Compliance export | Archiving and compliance depend on the Exchange and Skype archiving setup. Confirm the export path with your records team. | Compliance export is in paid Professional, Enterprise and Enterprise Advanced plans. Confirm the export format with your assessor. |
| Air-gapped deployment | Runs on premises in a disconnected network if licensing and updates are handled offline. Confirm update and licensing steps. | Air-gapped deployment is available in the Enterprise Advanced plan, per the Mattermost pricing page. |
| Enterprise voice (PSTN) | Enterprise Voice with Mediation Server and PSTN connectivity. Mattermost does not provide telephony, so a SIP or PSTN solution must come from elsewhere. | Not provided. Telephony requires a separate SIP trunk, PBX or contact center platform. |
| Meeting audio and video | Audio, video and web conferencing with the Enterprise CAL. Mattermost does not provide conferencing, so pair it with a separate video service. | Not provided natively. Pair with a self-hosted video service such as Jitsi, and confirm integration options. |
Where chat data lives and who controls it
Moving chat off Skype for Business Server changes where messages, identities and logs sit and who holds the keys. The cards below cover the decisions that follow from that move, from the datacenter and identity model to retention, licensing and the compliance evidence your own team must produce.
Data location in your datacenter
Mattermost runs as a single Linux binary with PostgreSQL as its database, so message content, file attachments and metadata can stay inside your datacenter or air-gapped network. Skype for Business Server stores its chat history in its own back-end database on your servers, so the data location question is similar, but the components differ. Confirm where file attachments, search indexes and backups land, because those copies often end up outside the primary database.
Hosting model and database
A single Mattermost server is simple to run, but high availability needs redundant application servers, redundant database servers and redundant load balancers, and that clustering is limited to the Enterprise and Enterprise Advanced plans. Plan the PostgreSQL operation, backups and failover yourself, since Mattermost does not run the database for you. Skype for Business Server treats its front end, back end and Edge roles as separate servers, so map each role to a Mattermost or PostgreSQL equivalent before cutover.
Identity from AD/LDAP and SSO
Skype for Business Server authenticates users through Active Directory, so identity and presence follow directory accounts. Mattermost gets AD/LDAP user sync and SSO (SAML, OIDC, OAuth) from the Professional plan upward, so you need a licensed tier to keep deprovisioning in step with your directory. The free Team Edition is aimed at teams that do not need single sign-on. Confirm how disabled accounts, group membership and guest access will be removed in both systems.
Retention and export controls
Retention in Mattermost is set by your administrators, and the free Entry tier caps channel message history at 10,000 messages, so a larger estate needs a paid edition for usable history. Skype for Business Server archiving depends on separate Exchange or Skype archiving configuration. Document the retention periods you need for regulatory and legal hold, and test whether exports cover direct messages and private channels before you rely on them.
Licensing for air-gapped use
Mattermost Enterprise Advanced is the tier that supports air-gapped deployment, while the free and lower paid tiers assume a connected environment for updates and licence checks. Mattermost sells prepaid annual subscriptions by seat count, so ask for the seat basis, renewal mechanics and how license keys are handled without internet access. Ask the same questions for any open-core component you add, since commercial licences may apply on top of AGPL code.
Compliance evidence you must produce
Chat controls only count as evidence when you can show them working: access reviews, retention settings, change logs and backup restore tests. DeployOpen prepares these controls, configurations and evidence for your assessment, but it does not issue audit reports, attestations or certifications, and independent auditors make that determination. Ask your auditor early which artifacts they will sample from the chat platform and who in your organization owns each one.
What Mattermost editions add over the free tier
The first decision is which build fits the estate. Mattermost Team Edition is free, open source and self-hosted, aimed at teams under 250 users that do not need single sign-on. Entry, the free tier of the commercial build, caps channel message history at 10,000 messages and has no compliance features or high availability. A Skype for Business estate with a retention obligation can reach that cap quickly, so check your user count, the message history your policy requires and whether you need SSO before you choose a path.
The paid editions add the controls that most on-premises estates depend on. Professional includes SSO over SAML, OIDC and OAuth, and AD/LDAP user sync, which lets Active Directory remain the source of users and group membership, as it was under Skype for Business. Enterprise adds high availability clustering and FIPS 140-3 compliance. Clustering requires shared file storage on Amazon S3, an S3-compatible service or NAS on every node, because local file system storage will not work correctly. Enterprise Advanced adds air-gapped deployment. Confirm with Mattermost which FIPS 140-3 scope applies to your build and configuration before you rely on it in an audit.
Mattermost licenses its source code under AGPL v3.0 and offers a commercial license from Mattermost, Inc. for organizations that cannot meet AGPL obligations, such as those that modify the server and offer it to users over a network. Have counsel review which path applies to your use. Mattermost does not publish prices for Professional, Enterprise or Enterprise Advanced. These are prepaid annual subscriptions priced by seat licenses, so ask for a quote based on a written scope that states your seat count, edition, SSO and directory sync, cluster topology, storage design and any air-gapped requirement, and confirm the license terms in writing. Mattermost pricing lists the plans.
What a move from Skype for Business chat to Mattermost involves
The sequence runs from inventorying chat use and retention needs through a datacenter cluster, directory sync, channel pilots and parallel running, ending with the retirement of chat roles on the Skype front ends. Each step closes with a check the team can confirm before moving on.
Inventory chat use and retention obligations
Your team, or a DeployOpen engagement scoped in writing, lists which Skype for Business features people use in practice: one-to-one IM, persistent group chat rooms, presence, file transfer and any archiving or compliance policy that applies to message content. Record who owns each retention obligation and how long records must be kept. Ask Skype for Business administrators which archiving or compliance recording was enabled, because that determines what history must be preserved. The step is done when you have a signed-off list of chat features in use and a retention requirement for each.
Decide the Mattermost edition
Compare the needs from the inventory against the editions. Team Edition is free and open source, aimed at teams under 250 users that do not need single sign-on. Professional adds SSO and AD/LDAP user sync, Enterprise adds high availability clustering and FIPS 140-3 compliance, and Enterprise Advanced adds air-gapped deployment, according to Mattermost's pricing page. Ask Mattermost for a written quote tied to your seat count, since its plans are prepaid annual subscriptions and it publishes no list prices. The step is done when the edition and its subscription terms are chosen and recorded in the project plan.
Build the datacenter cluster with shared storage
Your infrastructure or platform team deploys the Mattermost application servers, the PostgreSQL database, and the load balancers in your datacenter. For high availability, Mattermost requires redundant application servers, redundant database servers and redundant load balancers, and shared file storage on Amazon S3, an S3-compatible service or NAS mounted on every node. Local file system storage will not work correctly and risks corrupting files. Confirm the storage and backup design with Mattermost's deployment planning documentation before procurement. The step is done when a test cluster survives a single node restart without losing files or sessions.
Sync users and groups from Active Directory
Identity administrators connect Mattermost to your directory so accounts, deactivations and group membership follow the same source Skype for Business uses. Directory sync and single sign-on are included from the Professional plan, according to the pricing page, and SAML single sign-on is documented separately. Confirm with your identity team how account lifecycle events, such as leavers, will reach Mattermost. The step is done when a sample set of test users signs in through your identity provider and a deactivated test account loses access.
Pilot channels with a small user group
Recreate a few persistent Skype for Business chat rooms as Mattermost channels for a pilot group, and agree on channel naming, membership rules and who may create new channels. Test presence, direct messages, file sharing and mobile clients under real working conditions. Collect feedback on features that depend on Skype for Business integrations, such as calendar presence or telephony, because those will not move with chat. The step is done when the pilot group has used the channels for a defined period and the open issues are logged with owners.
Migrate or archive chat history
Mattermost's documented migration path covers Slack workspaces, converting a Slack export with mmetl and loading it with mmctl. The supplied facts do not cover a Skype for Business chat history export, so confirm with Microsoft and with Mattermost which export path, format and retention tooling apply to your Skype for Business archive. Where no direct import exists, many teams keep the archive read-only in its existing compliance store and start Mattermost history on cutover day. The step is done when the export method is confirmed in writing and a restore test on a sample conversation succeeds.
Move meetings and telephony to other services
Skype for Business also carries conferencing, voice and room systems, which Mattermost does not replace. Assign each function to a separate service, such as a self-hosted video conferencing platform for meetings and a separate telephony or SIP solution for voice, and confirm integration points with each vendor. Confirm with telephony and room system suppliers which Skype for Business dependencies must be re-homed before Edge and front end servers are removed. The step is done when every Skype for Business function has a named replacement and an owner.
Run both systems in parallel, then retire chat roles
Keep Skype for Business chat available while users move, with clear guidance on which system to use for which conversations and a fixed date for each team's cutover. Once adoption is steady and the archive is confirmed, remove chat and presence roles from the Skype front end servers, and retire Edge servers only after the replacement services are live. Coordinate the removal with Microsoft's documentation for your Skype for Business version. The step is done when no active chat traffic reaches the Skype front ends, the archive is verified, and the decommission record is signed off by the infrastructure and security owners.
Questions buyers ask before choosing Mattermost over Skype for Business Server
How much effort and time does a migration from Skype for Business Server to Mattermost take?
The effort depends mostly on how many users and persistent chat rooms you have, how much history you need to keep, and how many integrations sit on top of Skype for Business today. Mattermost itself is a single Linux binary with PostgreSQL as its database, so the server build is not the long pole. The longer work is usually identity mapping from Active Directory, deciding which persistent chat rooms become channels, retiring Edge servers, and running both systems in parallel during users' cutover. No duration figure is supplied here, so ask any implementation partner for a timeline tied to a written scope that lists your user count, rooms, integrations and retention rules.
Can our own team run the migration without outside help?
A team with strong Linux, PostgreSQL and Active Directory skills can often run a pilot alone, but production cutover usually benefits from people who have done a Skype for Business retirement before. The risks sit in areas where mistakes are expensive: directory sync scope, retention settings, and high availability design. If you choose outside help, DeployOpen plans, implements, hardens, backs up and documents self-hosted platforms in your own infrastructure under a fixed scope agreed in writing before work starts. Ongoing upgrades and support are available as retainers. Ask any provider to name which tasks they will hand over to your staff.
What does the work need from our staff after go-live?
After go-live, staff need to run upgrades, backups, user lifecycle tasks and monitoring, and they need someone who can read the Mattermost release calendar. Mattermost publishes a new server version in binary form on the 16th of each month, and the server releases page lists support end dates for each version, so an upgrade plan is a recurring task. Extended Support Releases, such as v11.7 with support ending 2027-05-15, give longer patch windows if your change process is slow. Confirm which on-call hours, database administration and Linux skills your team already has before you choose a support model.
Does Mattermost cover presence, calls and meetings the way Skype for Business does?
Mattermost covers chat, channels, direct messages and presence-style status for users, but it does not replace the telephony, room systems or conferencing that Skype for Business Server provided. Enterprise voice, dial-in, room devices and Edge-based federation need separate components. Plan a video service for meetings and confirm how any dial-in or room device connects to it. Check the exact presence and notification behaviour in the Mattermost documentation against your requirements, because the feature set differs by edition and version.
What do SSO and AD/LDAP sync cost by Mattermost edition?
According to the Mattermost pricing page, SSO (SAML, OIDC and OAuth) and AD/LDAP user sync are included from the Professional plan, and they are not available in the free Team Edition, which is aimed at teams under 250 users that do not need single sign-on. Professional, Enterprise and Enterprise Advanced are prepaid annual subscriptions priced by seat licenses, and the pricing page lists no public prices, so request a quote for your seat count. Costs recur each year, while the migration work is largely one-time. Ask the vendor which features each tier includes in the version you will deploy.
Does high availability need extra storage beyond the database?
Yes. Mattermost high availability uses redundant application servers, redundant database servers and redundant load balancers, and it is available only on the Enterprise and Enterprise Advanced plans. Each node must mount shared file storage, such as Amazon S3, an S3-compatible service or NAS, because local file system storage will not work correctly and risks corrupting files. Database read replicas and search replicas can scale concurrent users, with writes going to the primary database. Confirm the storage performance, backup and replication design with your storage team before you size the cluster.
Can Mattermost run air-gapped, and which edition does that need?
Air-gapped deployment is listed for Enterprise Advanced in the Mattermost pricing information, so an air-gapped estate should confirm that edition before design work starts. Disconnected networks also change how you handle updates, licence renewals and container or package delivery, because the usual online release flow does not apply. Ask the vendor to confirm in writing which artifacts you can import offline, how licence validation works without internet access, and whether your accreditation body accepts the build. Compliance readiness work, such as preparing controls and evidence, is something DeployOpen can prepare, but it does not issue audit reports or certifications.
How DeployOpen helps evaluate and implement Mattermost
DeployOpen is a Chainscore Labs company that plans, implements, integrates, hardens, backs up and supports self-hosted open-source platforms inside the client's own infrastructure, including their cloud accounts, data centers and air-gapped networks. For a Skype for Business Server estate moving to Mattermost, the first engagement is usually an evaluation of what the Skype deployment actually does today: which users rely on persistent chat, which group conversations need to become channels, which federation and external access paths are in use, and which telephony or room systems depend on the Skype front ends. That inventory decides which Mattermost edition fits, since SSO, AD/LDAP sync and clustering sit in paid plans, and it decides what has to be sourced elsewhere.
Implementation covers the Mattermost deployment itself on the client's servers, with PostgreSQL as the database and shared file storage that a high availability cluster requires, plus directory integration with Active Directory and the single sign-on configuration the chosen plan allows. Each of these items is a decision to record in writing: which AD groups map to teams, how deactivated accounts are handled, which SAML or OIDC settings the identity provider needs, and how backups and upgrades are scheduled against Mattermost's monthly server release cadence. Migration planning covers retention of archived Skype content, a parallel-running period and the order in which users move. Security testing of the deployed platform, its admin interfaces and its integrations can be scoped separately.
Engagements are fixed-scope, with scope, deliverables and timelines agreed in writing before work starts, and ongoing support, upgrades and continuous testing are available as retainers. DeployOpen does not publish a price list, and a quote follows from the written scope. To request one, send the Skype for Business Server version and topology, user count, the Active Directory forests involved, the identity provider in use, the telephony and room systems that connect to Skype, and any data residency or air-gap requirements. DeployOpen prepares systems, controls and evidence for compliance assessments but does not issue audit reports, attestations or certifications, so those remain with independent auditors and certification bodies.
