As with any professional correspondence, you don't want to seem too stiff or formal, like you're writing a letter from a Victorian template or a bad spam email asking someone to send money to a deposed prince overseas—but you also don't want to be too conversational. You're not in a dialogue yet, so it's important to treat this like a professional first interaction, and not like you're skipping several steps and asking to meet for coffee. The tone you're reaching for is, "You don't know me yet, but I'm interested in your company and want to tell you more about why."
Assess Your Final Draft At this point, you're ready to send it off, either in the mail, handing it off, or sending it through the Internet tubes. Let's take a last look at the good examples put together, Jean's better draft.