We have all experienced it. That moment when you read an e-mail and react emotionally to it. Some of us immediately send off a reply while still in the throes of anger. Others sit on it a while and carefully craft a reply. Very few of us pick up the phone or go to the person directly and ask them if our interpretation of what they were implying in the e-mail was correct.
The problem is tone, as we have no way of telling what it actually is from the words on the screen. It is left to us to add the tone and depending on our mood at the time and many other factors we can easily get it wrong. In my personal experience when that happens it is all down hill from there. People feel free to say things in an e-mail when they are angry that they would never ever have the balls to say to your face.
In the past I had a relationship seriously damaged because the only way the person would communicate with me was by e-mail. Once the flame war started there seemed to be no way to put it out. No matter how carefully I crafted my replies I was perceived as being hostile and to be fair I felt that the replies to me were incredibly hostile and nasty as well. Eventually I decided that I would only make matters worse by continuing so I just stopped.