Email is the most misused tool out there right now because so many people use it as a poor-man's collaboration tool.
I know people that set their preferences for email checking frequency to 1 minute beause they're afraid they may miss something. They ask everyone in the office to select unique email alert tones, and then turn up their speakers full blast and come running from down the hall (or even from another floor) if they think they heard their tone.
Yet in over 20 years of experience in the business, not one of those guys can cite an example of a negative event happening because they were 15 minutes late receiving an email.
It's simple really... Email is best for messages and prolonged conversations. IM is best for more quick questions or short conversations. And the telephone, VOIP, or webcam is by far the best for immediate and\or long conversations. Just use each tool for what it's best for and leave it at that.