BCC alert request

I have received a few emails that had BCCs on them, unbeknownst to me. I have replied to those emails. And then later, I have received copies from other recipients that show my whole thread to the original sender - that I thought was private. The person replying did not see my communication (as far as I know). But my mac shows the whole thread including the person that was responding so it is disquieting.

I understand that even if I had used "reply all" on the original that my reply would only go to the original sender. Not to any BCC. However, could the original sender, perhaps, forward the emails that I sent to them/him/her and not realize all the private communications were going along?

Could other recipients somehow see those communications in other ways?

Can I set up Mac Mail to let me know, alert me to the fact, that an email has BCC addresses on it. I don't need or want to know who they are - I just want to know if they/it exists so I can take a different route in a reply or at least know the original email was not just sent to me.

If there is NOT a setting like that - there should be. Simply an alert like "this email is also sent to other hidden recipients".