German State Swaps Exchange/Outlook for Open-Xchange and Thunderbird
Schleswig-Holstein has completed a full migration from Microsoft Exchange and Outlook to Open-Xchange and Mozilla Thunderbird — replacing more than forty thousand government mailboxes in roughly six months.Digital sovereignty in practice
According to the state’s digital ministry, the switch is part of a broader strategy to reduce dependence on foreign vendors and keep control over data processing. The project consolidated email, calendars, and contacts on open protocols (IMAP/SMTP, CalDAV, CardDAV) operated by a public IT provider, with web access via Open-Xchange AppSuite and optional desktop use through Thunderbird.What exactly changed
• Scope: 40k+ mailboxes and over 100M messages/calendar entries were moved to the new stack.• Clients: Webmail through Open-Xchange; many offices use Thunderbird for desktop; thousands of mobiles sync natively.
• Timeline: The cutover was executed in phases across ministries, justice, police, and agencies, reaching completion in early October 2025.
• Next steps: SharePoint alternatives (e.g., Nextcloud) and continued rollout of LibreOffice are planned as part of the same sovereignty roadmap.
Why it matters
For public administration, email is mission-critical. Moving it off proprietary groupware reduces licensing exposure and aligns with EU data-governance goals. It also creates a reference template for other states that want standardized, vendor-neutral collaboration built on open formats.Lessons from the migration
• Phased cutover: teams migrated by cohorts, keeping legacy mail available until validation.• Interoperability first: open protocols eased mobile and multi-OS support without lock-in.
• Change management: training and “web-first” workflows helped users adapt with minimal disruption.
Broader context
Schleswig-Holstein has been piloting LibreOffice and open-source platforms for years; the email switch unlocks further steps, including replacing proprietary document stacks and collaboration hubs. If replicated, this model could lower public-sector costs and strengthen resilience across EU administrations.Conclusion
In half a year, a large European administration moved off Exchange/Outlook without major outages — and did so to advance digital sovereignty. For governments and enterprises watching from the sidelines, the message is clear: at scale, open-source groupware is not just viable; it is operational.Editorial Team — CoinBotLab