Following iCal object is not delivered to the attendee (user1).
This event was created by user2.
BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
PRODID:"-//NONSGML HandCal//EN
BEGIN:VEVENT
UID:0a548a2e-0d54-4ad8-a245-4f7329b6b4b9
DTSTART:20151112T220000Z
DTEND:20151112T230000Z
TAT=NEEDS-ACTION;ROLE=REQ-PARTICIPANT;RSVP=TRUE;SCHEDULE-STATUS=1.2:urn:x
-uid:user1
TAT=ACCEPTED;ROLE=REQ-PARTICIPANT;RSVP=TRUE:urn:x-uid:user2
CREATED:20151111T202418Z
DTSTAMP:20151111T202418Z
SUMMARY:sham
TZID:America/Los_Angeles
X-CUSTOM-TEST:CUSTOM DATA
END:VEVENT
END:VCALENDAR