A. Windows Rights Management Services (RMS) has great functionality to strictly control how information is used. In Outlook, it can determine whether users can forward, Reply to All, cut and paste, and more. However, it requires the RMS infrastructure be in place.
Outlook and Exchange have some hidden flags that aren't exposed by the normal UI that can stop Reply to All and forwarding, and Microsoft Research has released an add-in for Outlook 2007 and Outlook 2010 to expose the functions. Download and extract it, run setup.exe, then restart Outlook.
Once you restart, you'll have two new buttons in your message composition window for Reply Options, as shown here. Easy!