Identify the URL of the scheduling Outbox 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 is needed for a client to determine where the scheduling Outbox collection of the current user is located so that sending of scheduling messages can occur. If not present, then the associated calendar user is not enabled for the sending of scheduling messages on the server.
<!ELEMENT schedule-outbox-URL (DAV:href)>