I am reposting this question since my previous thread did not get resolved and my service ticket is still pending.
I have added the user in the DTR permissions on the back end, added him as a 'mamager' on the event in question, and authorized access (own events only) for: event, location, CSV, records and emails. Additionally, I have given the user in question elevated permissions as 'author' for the purpose of being able to access the correct menu item from the front end.
Unfortunately the user does not have access to the mass email function from the front end, which is critically important.