Hello, there.

Currently, QuickBooks only supports Gmail accounts as an email senders. The option to customize this isn't possible.

Since you already sent feedback, our product engineers will review your suggestion. If they see this as useful, they can include this to our next updates. 
 

To manage your sales forms efficiently, check out this article: Customize invoices, estimates, and sales receipts in QuickBooks Online. 

If you have follow-up questions about sending out invoices using QBO, please add them in the comments below. We're always happy to help. Have a good one.