Thanks for sharing for your situation on this thread, Murray6.

Let me direct you to the best support for this issue. 

At the moment, there's an open investigation regarding the bounced invoice emails. You'll want to check out the details and the workaround shared by JD93 on this thread. 

I'd also recommend reaching out to our Customer Care Team, so they can add your company details to the affected user list. This way, you'll get notified once the issue is resolved. Please take note that our support hours for QuickBooks Online Plus, Essentials, and Simple Start starts from M-F 6 AM to 6 PM PT and Saturday 6 AM to 3 PM PT. For the Advanced version, we're available any time, any day.

Here's how you can reach out to us:

1. Click the Help icon located in the upper right-hand corner.
2. In the Search window, click the Contact Us button located at the bottom.
3. Enter your question and click Let's talk.
4. Choose either Chat with us or Have us call you.

If you have the new QuickBooks Assistant help update, you can follow these steps:

1. In your QuickBooks Online account, go to the Help > Assistant.
2. Type Talk to a human and enter what do you need help with.
3. Click No if none of the articles shared are helpful and select Chat with us or Have us call you.

Additionally, you can check out this article to help manage your invoices: Create invoices in QuickBooks Online.

Please let me know if you need help with other task in your QuickBooks Online account. We're always available to assist you.