There is email, there is spam and then there is replyall.
Replyall is internal spam.
Replyall is the slop that fills your inbox from co-workers needing reassurance about their contribution. Replyall is what happens when people don't think about who needs the information they are providing in response to a legitimate question or action.
I had to spend an hour deleting spam and replyall before I could start working this morning.