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Windows 10 have implemented calendars/contacts sync with open protocols: blocked in favor of proprietary Exchange

The Windows shell and core apps can sync with built-in CalDAV and CardDAV sync engine. However, this can’t be configured to work with the hundreds of hosted service providers or the tens of open-source implementations. Windows 10 has locked down its implementation of open standards to just allow the leading US providers Apple iCloud, Google, and Yahoo. Everyone else is expected to pay for Microsoft Exchange to have their users sync their data with Windows 10.