The History tab on a booking can confirm whether or not emails sent through EzTix were successfully sent, received and opened by a customer. Whether the emails were automated confirmations, reminders or post-event emails, OR custom emails or canned responses sent through EzTix, all will be visible in the timeline of the history tab.

Accessing the History Tab:

Global Event Management > Booking tab > select the booking in question > History tab

There you will find a chronology, from newest action to oldest action for the particular booking. 

I.e. In the example below, we can see when the order was placed, that the confirmation email was sent but not opened or clicked, it was then refunded, and a canned response was sent.