Creating custom Message Form. Issue with custom Icon

Hi,

I am trying to create a custom message form for Outlook. It should be
version independent supporting OL2000 and above. I created a simple custom
form with a MessageClass as IPM.Note.MyMessage. There is no script embedded
so far with the form which will be a task for the future. I am providing a
couple of icons of sizes 32x32 and 16x16 on properties page for large and
small icons respectively. After that I published the form to my Personal
Forms Library. Now I used this form to send emails to myself but the problem
is that neither the sent nor the received mails have the custom icons with
them. I am using Outlook 2007 for development. The MessageClass of these
emails are appropriately set to the MessageClass of my custom form. I
verified it with OutlookSpy. What could be the issue and where am I wrong ?
What are the icons in property page supposed to do if not replace the
open/closed envelop icons of email ?

Thanks,
Abhishek