A bit on the heavy side, but Nextcloud's agenda component is CalDAV and can access external CalDAV/ICS calendars. However its mail client will only access its own address book (which is CardDAV).
Xav
----
Cyrus Home Page: http://www.cyrusimap.org/
List Archives/Info: http://lists.andrew.cmu.edu/pipermail/info-cyrus/
To Unsubscribe:
https://lists.andrew.cmu.edu/mailman/listinfo/info-cyrus
