Importing a vCalendar file into a PersonalStorag (Outlook PST) does not set attendees

If I import the following vCalendar file:

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//think-e-solutions/dxl2vcalendar
BEGIN:VEVENT
DTSTAMP:20190401T090240
ORGANIZER;CN="Jochen Tuemmers":administrator@yourcompany.com
ATTENDEE;CN="required":mailto:required@yourcompany.com
ATTENDEE;CN="required01":mailto:required01@yourcompany.com
ATTENDEE;CN="optional":mailto:optional@yourcompany.com
ATTENDEE;CN="fyi":mailto:fyi@yourcompany.com
DTSTART:20190402T070000
DTEND:20190402T080000
SUMMARY:Meeting [repeating]
DESCRIPTION:Description
X-ALT-DESC;FMTTYPE=text/html:<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//E
	N"> <html> <head> <title></title> </head> <body> Description </body> </html>
CATEGORIES:category
RRULE:FREQ=DAILY;INTERVAL=1;UNTIL=20190405T235959
END:VEVENT
END:VCALENDAR

into an Outook PST file using this code:

String appointmentID;
    		
FolderInfo folderInfo;
Appointment appointment;
MailMessage mailMessage;
MapiMessage mapiMessage;
MapiCalendar mapiCalendar;

 		
appointment = Appointment.load(vCalendarFilename);

mailMessage = new MailMessage();
mailMessage.addAlternateView(appointment.requestApointment());

folderInfo = personalStorage.getPredefinedFolder(StandardIpmFolder.Appointments);
    		
if (folderInfo == null) {
   folderInfo = personalStorage.createPredefinedFolder("Calendar", StandardIpmFolder.Appointments);
}

mapiMessage = MapiMessage.fromMailMessage(mailMessage);
mapiCalendar = (MapiCalendar)mapiMessage.toMapiMessageItem();
    		
appointmentID = folderInfo.addMapiMessageItem(mapiCalendar);

the import works, but the attendee information is missing in the Outook event.

If I drag and drop the vCalendar file into the Outlook calendar, everything is fine.

Any idea why the import is failing?

Regards,
Jochen

@jochen.t,

Can you please share source files along with generated result so that we may further investigate to help you out.