So, this actually does work under the right conditions.
I had occasion to test it myself today:
- I was doing maintenance in our EU datacentre
- I unplugged and moved a provider circuit cable
- They emailed me and our team inbox (which creates a group inbox topic) to say the circuit went down
- I replied to the email they sent, including our team email address on the cc:
- My reply made it into the same topic as their original email
It’s hard to say where it went wrong for you without knowing your exact setup.