Schleswig-Holstein, Germany, has successfully transitioned its email and groupware systems from MS Outlook to an open-source solution using Open-Xchange and Thunderbird after six months of data migration. This migration is considered a significant achievement towards digital sovereignty and cost reduction. The state is now a leader in Germany regarding open-source solutions in the public sector. Schleswig-Holstein plans to further expand its open-source adoption by migrating desktop PCs to Linux.