Drowning in E-mail? Chances are you're part of the problem. "When a message has gone back and forth three times on the same subject, it's time to use the phone," says Mark Ellwood, author of Cut The Glut Of E-Mail (Pace Productivity Inc., 2002). The slim paperback is full of commonsense suggestions that companies would do well to adopt to keep E-mail productive. For instance: Avoid overpopulating "cc" fields in hopes of impressing the boss. And don't jump at every ping of a new message. "If you start instantly answering," Ellwood says, "you'll train people to expect instant responses."