Hi there, sancrisme.
Thank you for coming back to the QuickBooks Community. I'll be sharing details about the timeframe of the feature to be available. Then, ensure you can send feedback so your suggestion is forwarded to the Product Development Team.
QuickBooks is continuously improving the product's features to better meet the needs of our customers. With this, our engineering team is constantly working on new features that may be considered in the future. However, we are unable to provide a specific time frame as to when the option to run a report that indicates the delivered and undelivered invoices entries.
For now, I suggest going to the Gear icon in QuickBooks Online. From there, you're able to choose Feedback to submit a request to have a report that will show all the emailed invoices that were delivered and which ones bounced back. Any recommendations are sent to our engineer for consideration in future updates.
I'm also adding this article to further guide you in effectively managing your business using QBO: Help guide for QuickBooks Online. It contains topics about advanced accounting, banking, and payments to name a few.
Let me know if there's anything else you need help with. Know that I'm always here to help you anytime. Take care and keep safe!