I had a very frustrating miscommunication recently in making an appointment by email, where I thought the appointment had been confirmed and showed up, but the other person didn't, as they were still waiting for my confirmation. The exchange ended with:
Me: Merci, oui, [date/time] est bon pour moi.
Them: Très bien. Nous nous retrouverons à [date/time].
How should I have replied to this last message to make it 100% clear that the appointment is definitely confirmed and I will be there?