OK, so then the answer to my original question then, is that there in fact is NOT a way to rec'v notifications regarding invoice delivery issues? Correct?

We do not have an issue with our customer facing email. We just occasionally have invoices that are not sent to the customer due to various reasons, like an incorrect customer email, a rejected email or a server issue. When that happens, it would be nice to immediately be notified of the failure instead of just stumbling upon the delivery issue error by random chance days or weeks after we thought the email was sent.