The main function of NoReplyAll Outlook Add-In from Microsoft Research is to prevent people from doing a reply-all to your message, or forwarding it. The add-in uses a facility built into Outlook and Exchange that is more lightweight than information-rights management but is not exposed in the existing UI. The add-in also includes a check for common email errors, such as omitting attachments or subject lines.
Installing it adds a couple of buttons to the Outlook ribbon.
It works with Outlook 2007 and Outlook 2010.