Several years ago I was taking ICN classes. During one of our first classes, the tech person for the classes made it very clear that it was not acceptable to use all capital letters when you are emailing someone. That meant that you were shouting at them, and it wasn't acceptable behavior. During the first semester of classes, I had a technology question that I needed resolved. When I emailed the tech person, the reply came back in all capital letters. It made me feel pretty stupid, and it really lowered my opinion of that person.