Email notification whenever an email fails

[masberg]

As of today, we do not recieve any notification if we post invoices and the deliver of email fails. This could mean that our customers never recieves their invoices. In addition, we would have no idea if any invoices fails to be delivered. 

[navin]

I agree on this. I think there should be an event that can call out an email and/or third party API being called in order to track all the failures.