Hi AndrewPFF,

Thanks for joining the thread. We appreciate your feedback and see how essential it is to send a professional estimate email. That is a very good suggestion and I know a lot of customers can benefit on that. You can send a feedback to our product engineers so they can review this suggestion to add this feature to Quickbooks Online in the next update. If you have spare time, please also leave a feedback about it in the Gear icon then click Feedback. This is the quickest and most direct way to send improvements or suggestions to our system engineers.

You can also check it here for any product updates release every month based on the feedback and suggestions we received from our customers. 

Let us know if you have any other questions, we're here to help.