Linux-based groupware suite positioned as a drop-in Exchange replacement, built by owner-managed grommunio GmbH in Vienna.

grommunio is an open-source collaboration suite from grommunio GmbH, an owner-managed company founded in 2020 and registered in Vienna, Austria.

It speaks Exchange’s native protocols — MAPI over HTTP, ActiveSync, EWS — so existing Outlook and mobile clients connect without a migration project, which is what makes it a genuine drop-in replacement rather than a look-alike. Alongside mail, calendar, contacts, and tasks it adds chat, video conferencing, and file storage, and runs on-premises or through hosting partners for enterprises, public institutions, and service providers.