How to add attachment to an appointment?

 appointment.Attachments.AddFileAttachment(file.Name, stream);
 //appointment.Attachments[0].IsInline = true;   disabled in Outlook 2007

In OWA,I find the appointment has attachment mark in the calendar of creator,but it hasn't attachment mark in the send mail box.

When I deleted it,I found it has attachment mark.

How to show the attachment mark both in calendar and send mail box?

I mean let the mail recipient could view the attachment.