Hi there, @office65.
You've got me here to share some information about using your company email address when sending sales transaction in QuickBooks Online.
Currently, the ability to use your company email address to when sending invoices or any sales transactions isn't available in QuickBooks Online. This is because the transaction is generated from QuickBooks. As an alternative, you can send the invoices from QuickBooks into your email and send it to your customers afterwards.
I can see how this feature would be beneficial to you and your business. QuickBooks are constantly working on improving the product to meet your needs. I'll pass along this preference to our developers so this will be taken care of.
I'd encourage you to check out our QuickBooks Online Blog to be updated with the latest news and updates including product innovations. I've also included here an article that contains some workaround in sending invoices to your customers.
Please know that I'm just a reply away if you have any other questions with this concern. Helping you is my priority. Thanks for coming.