@JaneDave_I I don't think you're answering the question.

abrackin@ethin.o knows WHICH invoice had delivery issues. If the invoice was sent to TWO email addresses, they need to know WHICH email address did not receive the invoice.

Quickbooks Online used to show this information at the bottom of the invoice. That feature has been removed. Where can abrackin@ethin.o find which email address of the two that the invoice was sent to had the issue?