Do the person you're sending the email to a favor - skip the LLM and just email the prompt you would have used. If the email was going to be worth a damn the prompt would hve included all the context and information you needed anyway.
Nah, not for sending, for groking; for reading long threads/intent/goals/tasks/conflict etc.
Not yet, I think Google has a Workspace AI product that does that but we haven’t tried it