It's now 2025 and this feature request is at least 4 years old. I was searching around QB community for any updates and found the Customer Feedback site and there was a request for this feature back in 2019. Here's the site for anyone who wants to add their vote on that site https://feedback.qbo.intuit.com/forums/591862-quickbooks-invoice-payments-portal/suggestions/3671434.... 

Like @IT-IN-A-BOX stated, it's a security issue that someone could very easily pose as my business to send invoices. But also, we have had so many issues with customers not receiving our estimates and invoices consistently from the "[email address removed]" that I am now being required to go through the extra steps to generate estimates and invoices and then send them manually through my Outlook email. This is insane but it's more insane for me to tell our customers to just add the email to a safe sender's list repeatedly, I cannot do IT support for all our customers.

I've used the "Feedback" option within QBO and the Customer Feedback for QBO website so please don't tell me to leave my suggestion like you told @Cam-Int and the rest of us here. Seeing how there hasn't been any change, it feels like all we are doing is screaming into a void. --_(-_-)_--