At work, where everyone uses Outlook, I often just set up a "poll" for this (even for only 1 recipient - it's only a couple of clicks). It does rely on me being able to guess what their answer will be, but for things like "Please confirm you'll meet deadline X", it's fine.
Obviously, this doesn't work in non-homogeneous environments.
Obviously, this doesn't work in non-homogeneous environments.