A message that looks perfect on your screen may arrive completely jumbled on the reader's screen. An easy way to help avoid such problems is to limit the length of your lines to no more than 65 characters. If your email program doesn't automatically wrap text, press return after every 10-12 words to make sure your lines are short enough. There are ways to accent your words in email to add emphasis. Break your text into paragraphs of at most 7 lines each.
Nothing looks more boring than an entire long block of text.
Mix both big and small letters in your text. Put your reminder in the P.S. after your signature. Studies show that the P.S. gets read more than the body of your message. Use the spell check. You represent one of the most prestigious universities in the world, be sure your written communications reflect this expectation of excellence.