My guess is (that's how I would have done it)...
You first FW the Thread to your e-mail account then you save this message as
a .MSG. When you reply to the Group, using the news interface of your choice
you also attach the .MSG file you just saved on your local drive (using
Outlook).
Claude
>A user responded to a large email thread with his response and the rest of
> thread attached as an msg file. How is this done exactly?
>
> Thank you.