meeting properties are not preserved by outlook

Question

In a Outlook addin I want to set PS_INTERNET_HEADERS properties on outgoing emails/meeting requests. I can see that for meetings those properties are not preserved when I open the incoming meeting (I send it to myself) - the email header for my property does not exist and I cannot see the property in OutlookSpy. for regular emails (not meetings) properties are preserved fine.

I can also reproduce this behavior with OutlookSpy - I create a new meeting, in OutlookSpy I add a PS_INTERNET_HEADERS named property, and send the meeting to myself. when I open the incoming meeting the property is gone. (it also does not appear when I open the meeting from the SentItems)

Answer 1

When and how do you set the properties? Keep in mind that AppointmentItem is never sent. When you call AppointmentItem.Send, a new MeetingItem object is created and sent. You can only access it in the Application.ItemSend event handler.