Contacting agency appointees directly at Onboarding

We've been advised (helpdesk ticket 189678) that agency appointees' email addresses can't pre-populate onto certain tasks on the onboarding portal as they are the agency's candidate. We have to liaise with these candidates directly in the onboarding process anyway and at this stage the offer has been approved so it would be very helpful if these could pre-populate into 'Email to' field under various tasks in the onboarding process.