Hi there, @alex62. 

Thank you for posting to the Community.  

In QuickBooks, there's a default setting in sending email. We're unable to change it. I can see the importance of having the feature to set your own domain to send email. So I’ll take note of it and send them to our Product Development team. 

In the meantime, I recommend you visiting our Blog to learn what new updates are being rolled out, as well as additional references while working with QuickBooks. Here's the link: https://quickbooks.intuit.com/blog/  

 Please let me know should you need anything else. I'll be here to help.