That’s a strong statement, but it gets even better:
It might be possible for the US government to lean on the Australian government or other international legal body to compel us to hand over data but this likely to be an expensive, time-consuming and highly visible process. In our opinion those barriers make it extremely unlikely to happen.
All in all, FastMail just made a strong statement that they have no knowledge of active spying on their users, and from the sounds of it they are prepared to make a loud complaint about such requests. Good for them, not sure it matters, but good for them.