Hi @mauld-louie
To grant this permission you have to be an Exchange admin, and do it manually, there is no way to do it automatically using Power Automate as there is no Exchange connector so far.
My suggestion is to create a shared mailbox, and send the email from there, you can attach the email of the user who completes the form in the body or subject.
Hope this helps.
Kind regards.
Community Support Team - Anthony Amador
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.