I'm writing an application as plugin to Outlook 2003 using VSTO.
Now I have a big problem. I tried to add envid,notify and ret parameters to
message header (MailItem) programmically but I got stuck.
According to SMTP specification, envid and ret must be added to RCPT
command.

This line should look like this

MAIL RET=HDRS ENVID=QQ314159

and recipient like

RCPT NOTIFY=SUCCESS

The problem is how to add these parameters to message header. I looked into
vsto MailItem and Recipient classes and i didn't find appropriate solution.
Is it possible to do it using REDEMPTION libary, CDO or Extended MAPI ?

Thanks for any ideas