Thank you for this information.  My Tasks are blank and does not have the View the errors link.  I created a task hoping it would allow me to dig deeper into the invoice to figure out which of the two email addresses was bad, but it didn't.  Also, now I can't delete the task or mark it as complete.  

It seems like some functionality was lost in the upgrade.  This was a simple screen that was one of the first screens you saw (I believe on the Home screen).  One knew they had an issue the next day when logging into QBO. 

Currently, the only way this was brought to my attention is a customer emailed me from a statement and said they never received it.  I send my invoices from Recurring transactions and don't always go to the Customer section, which is one place to tell if the invoice had delivery issues.