what does it mean when one writes an email using all caps
All caps is used primarily for emphasis. When used excessively in an electronic message (email, discussion thread, etc), this is called shouting and it is considered quite rude. For more on the various uses of all caps, see the Wikipedia article.ontextual emphasis: Capital letters can be considered a third form of emphasis, among Italics and Bold text. They are used to denote a louder, almost shouting (and in many cases actually shouting) pronunciation.