Assessor email address not visible to students in the portal

Our assessors are independent consultants and have their own emails that are not linked to the organisation. We would prefer students were not able to see the personal email address of our assessors and that the 'conversation' remains within the portal. 

For example when they click the link to email the assessor it just has the assessors name and then sends an internal email to the assessor that is recorded in their file notes. The assessor would receive a workflow notification that they have an email and would need to log in to view the message. Then when they reply it sends an email to the student within the portal that they then have to log in to view. This will ensure that all communication is transparent and our admin team can be privy to all communications when managing any issues or follow ups.