I'm very sorry. But suggestion section is closed, and this should be very quick to implement, and I think half of email users would LOVE this feature (just never thought of it)
A pop up that asks me "ARE YOU SURE" every time I hit Reply All, to make sure I didn't accidentally hit Reply All instead of just Reply. Make it a selectable optional feature in the settings, default it to OFF so it doesn't bother people who don't want it.
I get an email almost every day where the person on the other end accidentally hits Reply All but meant to just Reply to the sender.
Thank you! And again, I'm sorry.