Guarantee of emails sent to customers

In my previous cart, some emails did not get sent to customers.

I just changed the status from Open to Processed with the Notify Users checked.

How do I guarantee my emails are getting sent - for anything ?

Thanks, Duaine

you just take test on self order and than try to send with the same method.

Well, what I’m really driving at - is there an email CC: back to the admin for each email ?

It is already cc there, once order was processed or open you will automatically get the customer invoice to your email address.