Schleswig-Holstein Harald Nachtmann/Moment/Getty ImagesFollow ZDNET: Add us as a preferred source on Google.ZDNET's key takeawaysSchleswig-Holstein has moved from Microsoft Exchange and Outlook to Open-Xchange and Thunderbird for e-mail.Other EU entities have opted for open-source alternatives.This switch isn't just a technical change; it's a political move.The German state of Schleswig-Holstein has dumped its government email and calendar systems for open-source software. The six-month migratio...