Reply To: Send Email copy to admin or to custom email

And why aren’t you sure? Didn’t some came on?
If you get the mail to admin and the address of the guest is correct it comes on, and if not you get a delivery error message.
In any cases a copy of the mail doesn’t help you at all as it isn’t implementing that your guest also got it.
To test the mails for working just add a reservation with your mail.