Good News! Germany's Schleswig-Holstein Completes Massive Migration to Open Source Email Systems

Germany's Schleswig-Holstein state successfully migrated 30,000 government employees from Microsoft Exchange and Outlook to open source alternatives Open-Xchange and Thunderbird. The six-month transition, completed in October 2025, moved over 40,000 mailboxes containing more than 100 million emails and calendar entries. Despite some initial challenges including downtime and delays, the migration represents a major step in the state's broader open source strategy, which previously included replacing Microsoft Office with LibreOffice across all state computers.