Communicate after a non-wrike user submits a form

Our legal team wants to receive literature review requests through Wrike. Non-wrike users can submit a document for review with the external form link and will get a confirmation email that their request was submitted. Great. BUT AFTER THAT... How do they get notifications if their literature has been approved/rejected, and how does the legal team communicate and ask questions from the non-wrike user? If they comment in the task, they can't tag the non-wrike user. Does the non-wrike user get emails with the activity in the task? How does this work? I've tried many tests but can't figure this out. Does the legal team have to get out of Wrike and email the non-wrike user with comments and approval?