Work in progress: The GroupDAV/CalDAV connectors are not released yet. Please stay tuned, we are close but not ready ;-)
ZideOne is working on solutions which integrate contact, event and todo list servers with Microsoft Outlook™.
The core is a MAPI Message Store Provider which maintains a write-through offline cache on a remote HTTP server.
Our core connectors synchronize Outlook data using the WebDAV, GroupDAV, CalDAV and CardDAV protocols. They utilize the vCard and iCalendar data formats to represent the data.