NoReplyAll Outlook Add-In
I’ve been asking for something like this for, at least, a decade.
The primary function of this add-in is to add a couple of buttons to the Outlook ribbon to prevent people from replying to all the recipients of 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.
NoReplyAll Outlook Add-In - Microsoft Research