The native Exchange drop-in replacement.
As sovereign as you.
Built in Europe. Email, calendar, contacts, chat, video and files on one platform. Run it on your own servers, in a private cloud, or have a certified partner host it for you.
- 100% European open source
- GDPR & ePrivacy oriented
- No vendor lock-in
- Full data ownership
All the collaboration tools you actually need
Email, calendar, chat, video, files. One platform, one login. Works with the desktop and mobile clients your team already uses.
- Shared Calendars & Scheduling
- Contacts & Global Address Lists
- Tasks & Notes
- Secure Chat & Video Meetings
- File Sharing & Online Office
Fully compatible with
- MAPI / HTTP · EWS · EAS
- IMAP / POP3 / SMTP
- LDAP / Active Directory
Built for digital sovereignty
grommunio helps organizations maintain control over their communication infrastructure and reduce operational dependency on large cloud platforms.
- 100% European open-source technology
- GDPR & ePrivacy oriented architecture
- No vendor lock-in
- Full data ownership
- Enterprise-grade security
- Flexible deployment — on-premises, private cloud or sovereign hosting
Your business data stays under your control — not in proprietary cloud ecosystems.
- 6 → 100,000+
- Users per deployment
- 200+
- Certified partners worldwide
- 100%
- Open-source technology
- EU
- Engineered for sovereignty
Works with any operating system
Native and web clients across every major platform — your users keep working the way they always have.
- Linux
- Windows
- Apple
- Android
Evaluate
Convince yourself with a demo
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Become a grommunio partner
Benefit from our partner program and bring digital sovereignty and open-source collaboration to your customers.
Frequently asked questions
Can grommunio be evaluated as an alternative collaboration platform?
Many organizations review platforms such as Microsoft 365 or Google Workspace when reassessing their collaboration infrastructure. grommunio provides an open-source communication platform supporting email, calendar, contacts, chat and file collaboration. The platform can be deployed on-premises, in private cloud environments or through certified hosting partners, giving organizations full control over infrastructure and data.
Can grommunio work with Microsoft Outlook and Exchange communication protocols?
Yes. grommunio supports widely used Exchange communication protocols such as MAPI / HTTP, EWS and Exchange ActiveSync. This allows organizations to continue using existing Microsoft Outlook clients while operating their collaboration infrastructure on their own servers or through hosting partners.
Is grommunio GDPR compliant?
grommunio is designed as a European open-source software solution that enables GDPR-compliant deployments. Actual compliance depends on the specific implementation, hosting model and organizational measures.
Where is grommunio data stored?
Data is stored exclusively where the organization operates its infrastructure — on-premises, in a private cloud or with a European hosting partner. grommunio itself does not store customer data.
Which industries and organization sizes is grommunio designed for?
grommunio is particularly suited for public administrations, healthcare organizations, educational institutions, financial service providers, and companies with high compliance and data protection requirements. The platform is highly scalable and can be deployed in small organizations starting from approximately 6 users as well as in large multi-tenant environments with more than 100,000 users. Based on a Linux architecture, open standards, and flexible deployment options, grommunio supports regulated industries, mid-sized enterprises, and international corporations alike.
Where is grommunio developed and based?
grommunio GmbH is headquartered in Vienna, Austria — at the DC Tower, Donau-City-Straße 7. All development happens in Europe, and the company is independent and owner-managed.
What's the relationship between grommunio and gromox?
gromox is the open-source engine — the set of services (gromox-http, gromox-zcore, gromox-midb, gromox-imap, gromox-pop3, gromox-delivery, …) that speak the Exchange-compatible and IMAP/POP3/SMTP protocols. grommunio is the complete platform built around gromox: the web applications (Web, Chat, Meet, Files, Office), the admin tooling, the gateways (grommunio-sync for EAS, grommunio-dav for CalDAV/CardDAV), and the enterprise components.
Is grommunio open source?
Yes. The core engine (gromox) and the surrounding components are released under open-source licenses on GitHub (github.com/grommunio) and Codeberg (codeberg.org/grommunio). A commercial subscription adds long-term maintenance, manufacturer support.
Proud part of the European open-source community
Built in the open
grommunio is developed entirely in the open — on GitHub and Codeberg, every commit and every release. Here's a live look at the last 90 days.
- 37
- Public repositories
- 1,055
- Commits · 90 days
Legal Notice: grommunio is an independent software product and is not affiliated with, endorsed by, or sponsored by Microsoft, Google, Amazon, Open-Xchange or any other third party. All product names, logos, brands and trademarks — including Microsoft 365, Microsoft Exchange, Microsoft Outlook, Google Workspace, Open-Xchange and Amazon Web Services (AWS) — are the property of their respective owners and are used solely for identification, comparison and contextual purposes. Their use does not imply any endorsement or affiliation.