Hello @KimD1782,

I appreciate you for joining us here in the Community space. Allow me to step in and assist you with your concern about the Undeliverable error message in QuickBooks Online.

Being able to automate the emailing of invoices is beneficial to QuickBooks users. An issue like this causes a delay in sending sales data to your customers and will affect your business too.

I recommend performing some troubleshooting steps to isolate and figure out the cause of the issue. Since the problem is happening to one client, let's delete and re-create the recurring transaction.

This way, we can check if the issue is related to the template. You'll need to add the client details again, including the same email address.

Here's how:

1. Click the Gear icon in the upper-right corner.
2. Select Recurring transactions under Lists.
3. Find the recurring invoice.
4. Press the drop-down arrow under the Action column, then select Delete.
5. Choose Yes.
6. Create a new recurring template for the customer.

Another troubleshooting you can try is to create the invoice manually. Check if you'll still receive the same error when performing the process in QuickBooks.

If the problem with the client invoice continues, please give us a call. Our QuickBooks Support Specialists will take over and help you further to get back on track.

They have the tools to review your account in a secure environment. Our support for Plus, Essentials, Simple Start is available from 6 AM - 6 PM PT (Monday - Friday) and 6 AM - 3 PM PT (Saturday). For Advanced, any time, any day.

Here's how you can reach them:

1. Click the Help tab in the upper-right corner.
2. Go to the Assistant tab.
3. Click Get help from a human.
4. Choose Chat with us or Have us call you.

Also, you can access the list of bounced emails with delivery errors within QuickBooks. For more information, I've attached the article I find helpful when emailing customers in QuickBooks: How to view list of bounced emails with delivery errors.

I'm always available if you have more questions or concerns about fixing error messages or emailing invoices. Comment below, and we'll get back to you. Take care.