Microsoft 365 alternatives for a sovereign office
Choose who operates your office suite and where data lives.
Compare suites and workspaces by who operates them, where data is stored and which Microsoft 365 jobs they actually replace — from open-source suites you run yourself to EU-region cloud services.
Editorial update: 19 October 2026
What should your next tool do better?
Microsoft 365 bundles several jobs: Outlook mail and calendar, Word, Excel and PowerPoint, OneDrive and SharePoint files, and Teams chat and meetings. A Microsoft 365 alternative rarely replaces all of them in one product, so list the jobs your organisation depends on before comparing suites.
Most European searches for a sovereign office start with a second question: who controls the service? Microsoft's EU Data Boundary commits to storing and processing customer data for Microsoft 365 in the EU and EFTA, with documented exceptions. A storage location is not the same as operating the service yourself. This guide compares openDesk, Nextcloud Hub, Proton for Business, Zoho Workplace, Google Workspace and Polybase. Polybase is our product and is labelled throughout.
A different tool for a different need
Start with your requirements, then compare the trade-offs.
Compare at a glance
| Explore the options | Best for | What to check |
|---|---|---|
| openDesk | Public bodies and large organisations that want an open-source Microsoft 365 replacement under their own operation. | Several integrated applications mean real operating effort, and each application keeps its own interface behind the shared portal. |
| Nextcloud Hub | Organisations that want a self-hosted file cloud with sync clients and are ready to build the rest of the suite around it. | You operate the platform: updates, office engine, app compatibility and performance tuning are your responsibility or your provider's. |
| Proton for Business | Small and mid-sized teams whose main concern is encrypted email and file storage with a Swiss-based provider. | End-to-end encryption limits server-side features and integrations. Check Docs and Sheets against your Word and Excel files, and plan for team chat and project work separately. |
| Zoho Workplace | Businesses that want a like-for-like cloud suite with mail hosting outside the Microsoft and Google ecosystems. | No self-hosting. Zoho's privacy FAQ describes rare support access by its Indian entity under Standard Contractual Clauses; review this with your data protection officer. |
| Google Workspace | Organisations that want a mature cloud suite and accept a US-based provider. | A Europe data region answers where data is stored, not who operates the service. Switching from Microsoft 365 to Google moves the dependency rather than removing it. |
| PolybaseOur product | Teams replacing Teams, SharePoint, Planner and shared inboxes with one workspace they can self-host. | Not a full Office suite: complex Word, Excel and PowerPoint files may change after conversion, and Polybase is a mail client, not a mail server. Not SOC 2 or ISO 27001 certified yet; native SAML is not supported. |
Six Microsoft 365 alternatives.
- Product website
openDesk
The public-sector open-source workplace
openDesk is developed by ZenDiS, the German Centre for Digital Sovereignty. It integrates open-source applications: OX App Suite for groupware, Nextcloud for files, Collabora for office editing, Element for chat, Jitsi for video, XWiki for knowledge, OpenProject for projects and Notes for collaborative notes.
- Best for
- Public bodies and large organisations that want an open-source Microsoft 365 replacement under their own operation.
- Hosting model
- Kubernetes-based; self-operated, as SaaS from cloud providers or with partners. Community Edition is free; Enterprise Edition is recommended for production.
- What to check
- Several integrated applications mean real operating effort, and each application keeps its own interface behind the shared portal.
- Product website
Nextcloud Hub
Self-hosted files, groupware, office and calls
Nextcloud Hub combines Files with Talk for chat and calls, Groupware for mail, calendar and contacts, and Nextcloud Office for collaborative document editing. It runs on your own servers, at a hosting provider or with an Enterprise subscription.
- Best for
- Organisations that want a self-hosted file cloud with sync clients and are ready to build the rest of the suite around it.
- Hosting model
- Self-hosted (AGPL open source), hosting providers or Nextcloud Enterprise.
- What to check
- You operate the platform: updates, office engine, app compatibility and performance tuning are your responsibility or your provider's.
- Product website
Proton for Business
End-to-end encrypted mail, drive and documents
Proton for Business covers Mail, Calendar, Drive, Docs, Sheets, Pass, VPN and Meet on its Workspace plans. Proton is based in Switzerland and states that its workspace is end-to-end encrypted by default.
- Best for
- Small and mid-sized teams whose main concern is encrypted email and file storage with a Swiss-based provider.
- Hosting model
- Proton's hosted service; no self-hosted edition.
- What to check
- End-to-end encryption limits server-side features and integrations. Check Docs and Sheets against your Word and Excel files, and plan for team chat and project work separately.
- Product website
Zoho Workplace
A complete cloud office suite
Zoho Workplace includes Mail, Calendar, Cliq for chat, WorkDrive for files, Writer, Sheet and Show for office documents and Meeting for video calls. Accounts registered in Zoho's EU data centre use the zoho.eu domain.
- Best for
- Businesses that want a like-for-like cloud suite with mail hosting outside the Microsoft and Google ecosystems.
- Hosting model
- Zoho's cloud only; EU data centre available.
- What to check
- No self-hosting. Zoho's privacy FAQ describes rare support access by its Indian entity under Standard Contractual Clauses; review this with your data protection officer.
- Product website
Google Workspace
The main cloud suite alternative
Google Workspace covers Gmail, Calendar, Drive, Docs, Sheets, Slides, Meet and Chat. Supported editions can store covered data in a Europe data region; data processing settings and client-side encryption are limited to selected editions.
- Best for
- Organisations that want a mature cloud suite and accept a US-based provider.
- Hosting model
- Google's cloud only; data regions on supported editions.
- What to check
- A Europe data region answers where data is stored, not who operates the service. Switching from Microsoft 365 to Google moves the dependency rather than removing it.
- Product website
Polybase
Our productThe sovereign team workspace
Polybase brings chat, calls, tasks, docs and wikis, Drive files, an email client, calendars and Tables into one workspace. DOCX, XLSX and PPTX files can be opened and edited beside the channel discussion. Calls use WebRTC through a self-hosted LiveKit media server, encrypted in transit (DTLS-SRTP). Core is €10 per user/month; Email and Tables are add-ons.
Full disclosure: Polybase is our product. Read this entry as the maker's perspective — the caveat below is as real as everyone else's.
- Best for
- Teams replacing Teams, SharePoint, Planner and shared inboxes with one workspace they can self-host.
- Hosting model
- EU-region cloud, private VPC or self-hosted. Runs fully offline; calls use a self-hosted LiveKit server inside the same network.
- What to check
- Not a full Office suite: complex Word, Excel and PowerPoint files may change after conversion, and Polybase is a mail client, not a mail server. Not SOC 2 or ISO 27001 certified yet; native SAML is not supported.
Five questions before you replace Microsoft 365.
- 01
Which Microsoft 365 jobs does it replace?
Mail, calendar, Office editing, files, chat and meetings are separate jobs. Map each one to a tool instead of assuming one suite covers all of them.
- 02
Who operates the service?
A vendor cloud, a European provider or your own team. The operator decides who can access data, apply updates and respond to legal requests.
- 03
Where is data stored and processed?
Read the residency documentation for exceptions: support access, sub-processors, logs and features that run outside the chosen region.
- 04
How well does it handle your Office files?
Test real documents with tracked changes, formulas and complex layouts. Format compatibility is where most migrations stall.
- 05
What does running it cost?
Compare licences together with hosting, administration, support and migration effort. Open source removes licence fees, not operating work.
Start with your requirements, then compare the trade-offs.
Split Microsoft 365 into the jobs you actually use
Start with an inventory: mailboxes and shared calendars, Word and Excel files with macros or complex layouts, SharePoint sites and permissions, Teams channels and meetings, and the identity provider behind sign-in. Each job may land in a different tool, and that is often the more realistic plan than a single replacement.
Office editing is the hardest job to move. Suites built on Collabora Online, like openDesk and Nextcloud Office, focus on editing Office formats in the browser. Polybase opens and edits DOCX, XLSX and PPTX files and keeps them next to channel discussions and tasks, but advanced layouts, formulas or effects may change after conversion. Teams that author complex workbooks every day should test their own files before deciding.
Data residency is not the same as operating the service
Microsoft's EU Data Boundary, Google Workspace data regions and Zoho's EU data centres all address where data is stored. Each has documented limits: Microsoft lists transfers that continue outside the boundary, Google's processing setting is available on selected editions, and Zoho describes rare support access by its Indian entity under Standard Contractual Clauses. Read those documents with your data protection officer rather than relying on the region name.
Self-hosting changes the question. With openDesk, Nextcloud or self-hosted Polybase, your team or a chosen provider operates the infrastructure, keys, backups and updates. That is more control and more work: plan patching, monitoring and restore tests. Polybase is designed around GDPR principles; GDPR obligations stay with your organisation wherever the software runs.
A practical pilot before you leave Microsoft 365
Pick one team and one month of real work. Move a mailbox or shared inbox, a project folder with representative Word and Excel files, and the team's recurring meetings. Check calendar invitations with external guests, file sharing with a partner and sign-in through your identity provider.
Polybase connects existing Microsoft 365 mail accounts through OAuth, so a team can work in Polybase while mail stays with its current provider during the transition. There is no automated Microsoft 365 importer; migration assistance is available during onboarding. Tenant administrators can configure OIDC SSO and SCIM 2.0 provisioning; native SAML support is not included.
Where Polybase fits
You are reading this list on our site, so here is the part vendors usually skip.
When it fits
One workspace instead of a constellation
Chat, calls, tasks, docs, files, email and calendars share one workspace and one permission model, instead of Teams, SharePoint, Planner and Outlook administered separately.
Your choice of operator
EU-region cloud, your own VPC or self-hosted on your servers. With self-hosting your team holds the data and the encryption keys.
Office files beside the work
DOCX, XLSX and PPTX files open and edit next to the channel, task or thread they belong to, with version history for documents.
AI on your terms
Bring your own model — Anthropic, OpenAI, Gemini or self-hosted via Ollama. Your content isn't used to train foundation models.
What to check
Office authoring depth
Advanced Word layouts, Excel formulas and PowerPoint effects may change after conversion. Heavy spreadsheet and document authors may keep an office suite alongside Polybase.
Mail hosting
Polybase is an email client that connects to your provider through IMAP/SMTP, OAuth or a provider integration. You still need a mail provider or relay for your domain.
Certifications
Not certified yet — SOC 2 and ISO 27001 are on our roadmap. We answer security questionnaires and architecture questions today.
Migration tooling
No automated Microsoft 365 importer yet. We offer migration assistance during onboarding; automated importers are on the roadmap.
Replacing Microsoft 365.
What is the best Microsoft 365 alternative for European organisations?
It depends on the job and the operator. openDesk and Nextcloud Hub are open-source suites you can run yourself. Proton for Business focuses on encrypted mail and files. Zoho Workplace and Google Workspace are cloud suites with EU storage options. Polybase replaces Teams-style collaboration, tasks and docs in one workspace you can self-host, but is not a full Office suite.
Is the Microsoft EU Data Boundary the same as a sovereign workplace?
No. The EU Data Boundary is Microsoft's commitment to store and process customer data for its enterprise online services in the EU and EFTA, with documented exceptions. Microsoft still operates the service. A sovereign workplace usually means you or a provider you choose operates the software, so you control infrastructure, keys and updates.
Can Polybase replace Word, Excel and PowerPoint?
Partly. Polybase opens and edits DOCX, XLSX and PPTX files and keeps them with the related channel and tasks. Advanced layouts, formulas or effects may change after conversion, so review important files. Teams that author complex Office documents every day may keep an office suite alongside Polybase.
Is Polybase GDPR compliant?
Polybase is designed around GDPR principles, and self-hosting lets you decide where data is stored and who operates the service. Compliance depends on how your organisation uses and documents the software. Polybase is not SOC 2 or ISO 27001 certified yet; both are on our roadmap.
Can we move away from Microsoft 365 step by step?
Yes. Many teams start by replacing Teams, Planner and shared inboxes, while mail stays with its current provider. Polybase connects Microsoft 365 mail accounts through OAuth during the transition. There is no automated importer yet; migration assistance is available during onboarding.
Documentation and primary sources
Sources reviewed on 26 October 2026. Check edition, region and plan details with each vendor before purchasing.
- Microsoft: what the EU Data Boundary covers
- Microsoft: suites with and without Teams
- openDesk: components and deployment requirements
- openDesk: operating models and editions
- Nextcloud Hub: Files, Talk, Groupware and Office
- Nextcloud Server: AGPL licence
- Proton for Business: plans and encryption
- Zoho Workplace: included apps
- Zoho: EU data centre and support access
- Google Workspace: data regions
- Google Workspace: client-side encryption
Product names identify the tools being compared. No endorsement is implied.
See which Microsoft 365 jobs Polybase can take over.
Book a 30-minute demo and we'll map your Microsoft 365 setup onto one workspace — or read how we approach data sovereignty first.
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