Just wanted to add my voice to the group. It's been 4 years since this original post and QBO still only allows Google integration. I've used the feedback option multiple times and I've even gone to the Customer Feedback for QBO website and found a post from 2019 about this issue. Here's the site for the suggestion someone previously made https://feedback.qbo.intuit.com/forums/591862-quickbooks-invoice-payments-portal/suggestions/3671434.... It looks like this is an option in QB Desktop but for whatever reason it's not capable in QBO, which I find it hard to believe that in 6 years technology hasn't advanced to the point where this can be a feature online.

I have customers who are not receiving the estimate/invoice emails because the QB/intuit notifications email gets caught in their company's spam filter. It's unrealistic for me to provide my customers with a walkthrough of how to add that email to safe sender's list or expect them to even do it if I do. So QB where are you actually listening to your customers, here or on the Customer Feedback site? Because it doesn't seem like it's either.