Scientists have studied examined 16 billion messages sent by two million people in the largest email study ever conducted.
University of Southern California researchers looked at a random sub-sample of Yahoo Mail users worldwide, and only included users who had actively opted in to being in such studies. Emails from those not on Yahoo Mail were removed to avoid invading privacy.
They found that the best time to send an email was in the morning - with the worst times being in the afternoon, evening or weekend. And they found that the median time it took a teenager to reply to an email was 13 minutes - while those who were 51 and older took 41 minutes.