Identify the URL of the scheduling Inbox collection owned by the associated principal resource.
This property MAY be protected.
PROPFIND behavior: This property SHOULD NOT be returned by a PROPFIND DAV:allprop request (as defined in Section 14.2 of [RFC4918]).
COPY/MOVE behavior: This property value SHOULD be preserved in COPY and MOVE operations.
This property allows a client to determine where the scheduling Inbox collection of the current user is located so that processing of scheduling messages can occur. If not present, then the associated calendar user is not enabled for reception of scheduling messages on the server.