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All-in-one secure chat app for teams, friends and organisations. Keeps conversations in your control, safe from data-mining and ads. Talk to everyone through the open global Matrix network, protected by proper end-to-end encryption.
SOGo is a fully supported and trusted groupware server with a focus on scalability and open standards.
Part of the Mailcow stack.
Nextcloud is an open source, self-hosted file share and communication platform. Access and sync your files, contacts, calendars and communicate and collaborate across your devices.