Human -> Human (think we have this sorted)
AI -> Human
AI -> AI
If you are doing AI -> Human, then you need to be curating the response and understanding what it is saying, also, make sure its not leaking internal details or committing you to have phone calls/video chats (it does that). This works really well for the most, and humans respond with requested content. Quite often my AI debugs problems with their systems which I know little about. But humans do odd things like send screen shots of logs rather than text (they also leak internal details of their systems they potentially shouldn't). I used to tell people the content is partly AI, but now I just send the curated email without mentioning AI.