Why not just have an easy button that you can click saying Do Not Allow Reply All?
I know that there are some ways you can limit reply-all availability, like in the URL linked here. But there’s a note: If recipients open this email in other mail applications except Microsoft Outlook, such as opening on web page via web mailbox, they can reply all this email.
I’m semi-tech savvy but I’m no programmer. It feels like it should be easy to do, so either I’m totally wrong or email services are really missing out on a great thing they could do.
People in my organization do this, and it’s great. The only downside to that is when you want recipients to know exactly who else the email was sent to. Not super common, in my experience, but it does occur.
When I do bcc to a big list, I describe the distribution in the email header. Like “To: all users of the xxx application” or “To: All Engineering employees at the yyy site.”