In my view, there is no place for typing in all caps or using formatting to reflect emphasis in business emails. There is always an alternative in your choice of verbiage that can get your point across with the intended importance. Using all caps is perceived by many as yelling or shouting and certainly is not a professional way to communicate.
Same goes for when you are marketing your business in forums, discussion boards and on Blogs. Many online forums now allow users to post messages with added smileys, and to format their text for font, size and color. For business efforts, this is clearly a situation of just because you can doesn’t mean you do. Let your command of the written word get your point across without having to use formatting to do so for you.
Intent is intent. Caps means yelling, making things bigger, bolder and in red type would indicate a strong comment or trying to make a point. If you ask anyone to read out loud an email with such formatting, they will almost always raise their voice when reading capped or larger, bolder, red text. When you use such tactics you are leaving the level of emphasis to be determined by the other side — and that’s risky at best.
Learning how to communicate without formatting is a true skill and one few make much effort to hone. To be able to communicate with clarity simply by the words you choose and how you choose to use them without relying on bolding, font size, caps or colors is the true sign of a skilled communicator and a true professional.