After New Mail Has Arrived and setting of the From Field

I wrote an “After new mail has arrived” agent to notify my customers when an email address changes. If they mail john.doe@mydomain.com and John was replaces by Jain the agent will forward mail to Jain.Doe@mydomain.com and reply to the sender that John has been replaced by Jain.
I can’t get the “From” to be Jain.does@mydomain.com when the reply is sent. See following code;

'Now make the mail look as if its being sent from The new contact instead of the agent signer (defined in FWDTo) <== This don’t seem to be working

	Call RMDoc.replaceitemvalue("Principal",FWDTo)

	Call RMDoc.replaceitemvalue("ReplyTo",FWDTo)

On the receiving side teh mail looks like

And the details are