MAPI properties with a specific GUID are transformed into x-headers when the
item gets sent out, transformed by the message transport from a property
into part of the header. That's the only time that happens. You can grab and
existing PR_TRANSPORT_MESSAGE_HEADERS string and manipulate it using string
functions to add something and write it back. That's about it.

Why not just create an Outlook UserProperty, or if you don't want it to be
available to users create a named MAPI property and use that?

--
Ken Slovak
[MVP - Outlook]
http://www.slovaktech.com
Author: Professional Programming Outlook 2007.
Reminder Manager, Extended Reminders, Attachment Options.
http://www.slovaktech.com/products.htm


"Ashish" wrote in message
...
Yes i did same. I get value for PR_TRANSPORT_MESSAGE_HEADERS and search
x_header when open item. Then get the value for x_header and remove it. It
works successfully. But when i close item i get value for
PR_TRANSPORT_MESSAGE_HEADERS and set the value of x_header which i
delete.This i do because when i open mail next time x_header should be
there. But this time the value is not set. I tried to set it in
item_close/inspector_deactivate event but value is not set. While if i
debug the program step by step the value is set. Please suggest from where
i should set it when close the item.