an update on my query with thanks to Mike Richardson at Manchester Uni. for his assistance. It looks as though Entourage will only authenticate if exim advertises it. I have auth_advertise_hosts disabled for local domain addresses which is why it wasn't working from here. As Mike also pointed out, it doesn't work with TLS enabled in Entourage either.
Clive McDowell
Information Services
The Queen's University of Belfast
