I’m not sure if this should happen or not, but most other invoicing systems I’ve used give me a notification when a cient views their invoice in the email the system sent them.
With Invoice Ninja, it seems the “X client has viewed invoice Y” notification only happens when they view the invoice in the client portal.
Is that the intended functionality? If so, are there any plans to add that tracking pixel to the email? That would be a much truer example of “viewed”, since most clients paying by check would have no reason to click through to the portal since the PDF is attached and they can view/print it from email.