How your words look can be as vital as what they say. What your readers see at first glance will either turn them on or off. If the sentences and paragraphs appear too hard to read, people will not want to struggle to get the message. Paragraphs define coherent units of thought and make it easier for people to read messages. Don't use all uppercase letters.
All uppercase letters are hard to read.
Don't use only lowercase letters. The keyboard has a shift key. Don't use very long lines. Many mail readers cannot handle lines longer than 80 characters. If the system being used issues paragraphs without line breaks, output the message with line breaks.