Rules to detect mail failure

Good morning.

First, this module works perfectly and thanks for that!

What I would like to know is how to detect sending failure due to incorrect $to email.
Others checks could be done (timeout to SMTP, wrong $from) but if we assume that settings are correct, one thing we can not assume is that $to is always correct as generally set by end users.

So is there a way to add rule event for that?
- Queue Mail > Email failed
or
- Queue Mail > Email processed with then a "Sent Status" variable?

If I get any direction, I could work on building such a feature first for D7 then we will see for D8.

Thanks.