I would add that often it is effective to write a reply immediately (ie get it out of your headspace)...but save it in your drafts folder, and send it only the next morning.
This way you avoid much of the 'email ping pong' which is a real time-sink.
It's even more efficient to wait until the next day to write the reply, since you might not need to reply at all. A large percentage of the people who ask me questions at work manage to figure out the answer for themselves if I don't reply for a couple of hours (and they might even learn something by finding the answer on their own).
This way you avoid much of the 'email ping pong' which is a real time-sink.