AppointmentItem.UserProperties Lost on Recipients Not in Organizer's Domain

Question

Outlook 2010 Setup: Exchange Account #1 (Domain A) Exchange Account #2 (Domain A) Exchange Account #3 (Domain B)

Windows 8 Enterprise machine. I am logged into Domain A. I get receive/send email on all Exchange accounts. Whenever I create a meeting request the custom user property values are not read by Exchange Account #3. There are null or blank values.The code is suppose to populate for region controls on this.FormRegionShowing event. The 2 domains are federated with each other. I am stumped.

Textbox1.Text = (string)appointmentItem.ItemProperties[PropertyVariables.Property1].Value;
Textbox2.Text = (string)appointmentItem.ItemProperties[PropertyVariables.Property2].Value;
Checkbox1.Checked = (bool)appointmentItem.ItemProperties[PropertyVariables.Property3].Value;

Answer 1

This is to be expected - when a meeting invitation/update is sent through SMTP it is converted to iCal and all MAPI specific properties are stripped.

You can try to set a special UseTnef MAPI property (DASL name http://schemas.microsoft.com/mapi/id/{00062008-0000-0000-C000-000000000046}/8582000B) using MeetingItem.PropertyAccessor, but you can do that only in the Application.ItemSend event (since MeetingItem is created by Outlook, not your code).