Email not sending. Shows as "delivery error"

Hello there, Cliff. I'm here to help you surpass the email delivery error you received in QuickBooks Online (QBO).

To ensure we're on the same page, can you verify the specific transaction to which the QBO reported the error? Any extra information is appreciated to help us fix the problem. 

The Delivery error can be caused by attachments on your transaction or the way your Company email information is set up.

Let's ensure the company email and all customer-facing email fields are complete, have the correct format, and do not contain prefixes. You can check out the example below:

Wrong: email:mycompany@mycompany.com

Right: mycompany@mycompany.com

Additionally, if you use location tracking, check the email address format of the location you used on the sales form. If not, then skip to the next section.

1. Go to Settings ⚙.
2. Select All lists, then Locations.
3. Find the location you used on the invoice.
4. In the ACTION column, select the dropdown, then Edit.
5. Check your email address in the field “This location has a different email address for communicating with customers” and make changes if needed.
6. Select Save.
7. Try to resend your sales form.

For more troubleshooting steps to fix the issue of delivery errors, you can check out this article: Delivery Errors When Trying To Email A Sales Form.

Let me know if you have additional questions by commenting below. I'll be right here to answer your concerns.