Hi stephan2,
Conducting business in a digital age means that sending messages back-and-forth with clients is all done through the cloud. It can be difficult to confirm whether our messages were sent, received, or viewed. This is why QuickBooks Online lets you know when a customer has viewed their invoice. This is especially important with invoices, as there's usually terms and agreements on when payment is expected.
I can appreciate why you'd like this information to be displayed on estimates and quotes as well. I think this would also serve a valuable purpose by giving you the assurance that your message was received. At this time QuickBooks will only generate this information for invoices, however I'd be happy to pass along your feedback to the right people. Our software development team is committed to implementing new features that our customers suggest, and they take your thoughts and opinions seriously.
In the meantime, I'd recommend organizing a strategy with your clients to ensure that they've received your quote. For example, you can let them know that it's being sent, and if they haven't received anything in 2-3 business days, you'll have to re-send. This is completely up to you, and depending on your business this may or may not work. I'm simply offering a suggestion for potential workarounds.
I hope this helps, and please let me know if you've got any other questions.
Have a great day!
