E-mail is an excellent tool for exchanging quick updates, detailed factual information, schedules, sending notes, or attaching lengthy documents rather than printing them.  It is NOT a good tool for group discussion on a controversial topic, or for trying to make a point in a disagreement.  Yet, that is how it is often used, and co-workers and groups often find themselves in a major conflict created by an e-mail exchange.
 

I recently attended a meeting where attendees were trying to find common ground on an issue where several attendees had widely differing views.  We already knew this because in the week prior to the meeting, e-mails had been going back and forth between the opposing parties adamantly stating their opinions. And to ensure an audience, the writers cc:ed copies to the entire e-mail list of meeting attendees.  Lines had already been drawn as to who believed what, and the meeting started with arms crossed and attendees busy trying to figure out who had written what e-mail. 
 
Sitting alone in front of a computer giving your opinion with unlimited amount of time and no opportunity for anyone to counter your arguments gives you the illusion that anyone reading it is sure to see the validity of your argument. Instead, all that happens is an e-mail is soon sent back countering the first e-mail, which is then countered with another e-mail, which is then added on by someone on the cc list, and on it goes....
 
It is hard to have a live discussion with someone you are having a disagreement with, but if your goal is to move past the argument, you need to talk to the person. In the case of a group, that is what a meeting is designed for, and you should present your opinions at the meeting, not start an e-mail war beforehand. 
 
So if you find yourself poised over your keyboard, furiously determined to set the record straight; stop.  Ask yourself how you can have this conversation with real live people, and make the more difficult choice of open discussion.