Appointment EMail Confirmed Notification

Originally When I set it to YES for Send Confirmation email, It would send user an email confirmation message even though I haven't approved yet.
So what I did I set it NO so that once I approve it can send the email then. But it seems it;s not sending an email?

I could manually email it but I'm wondering if there is an option to send email after I approve it.
I've notice there is an option for admin to open a pending appointment and in there I see
Confirm "----" (Re)send confirmation email

Also I like to know if I can use my own HTML message when sending confirmation? Only way this can happen is if I set it to NO and then send manually. But with automatic is there way to send it in HTML with little design to it?