You're in the right place, @parind-phadte.

I'm here to help you add email addresses when sending invoices in QuickBooks Online.

QuickBooks Online sends your sales forms to the email address "QuickBooks@notification.intuit.com." It is a method to keep you updated on the status of your invoices that have been sent out. The program will notify you when the sales transaction form has been read, sent, or paid.

Furthermore, changing the default email from (quickbooks@notification.intuit.com.) isn't possible. Since this is to safeguard your account and avoid security risks.

We can also provide feedback to help make this feature available in QuickBooks Online. Refer to this article: How do I submit feedback?

Alternatively, you can use Gmail to send your invoice to your customer by connecting your Google account to your QuickBooks account. 

I'm adding this page for the detailed steps to personalize your sales forms. Customizing the look and design can be an effective way to improve your company's communications. Get some ideas here: Customize invoices, estimates, and sales receipts in QuickBooks Online.

If you have any further questions about the invoice email address, please tag me in your response. I'm always willing to lend a helping hand!