Filling out forms is I think one of the biggest use cases for computer use agents. We're working on some stuff to specifically make that use case faster and more accurate
Regarding monitoring a specific inbox, and auto-responding, you could also set-up an agent to do that, but I would advise having the agent automate more formulaic/simple emails rather than having it use too much of its own judgement when writing the copy for these emails. You can also add in checks for the agent to check in before you before hitting send