It's Sunday afternoon, I'm sitting in front of the fire, watching football, so it's time for a rant. Let me just say, that in 2004 plaintext email is obsolete.
First and foremost, if you cannot see HTML-formatted email, then you're using the wrong email client. Don't send me email (plaintext or otherwise) extolling the virtues of pine or eudora 1.0 or your favorite program from 1993. If your client cannot display formatted email, then you're totally behind the curve. This is a platform-independent observation, it doesn't matter whether you use Windows or Mac or Linux or whatever - I promise there is a client that can render HTML email. Heck, my Treo phone can render formatted email. You don't watch black-and-white TV, do you?
Next, if you don't send HTML-formatted email, then you're behind the curve. You don't have to use eight different fonts and colors and lines and boxes (although it might help you communicate). You don't have to include diagrams and pictures (although it might make your email more interesting). But you need the basics; paragraphs, italics, underlines, proportionally spaced fonts with serifs. How lame is it when you get a plaintext email and the lines wrap in funny places for no reason? You don't type memos on a typewriter, do you?
Even free online email services like Hotmail and Yahoo let you send and receive HTML-formatted email (sometimes they call it "rich text"). Heck, even AOL lets you format email. It might not be the default - you might have to change your options to turn it on - but you should. If you're sending plaintext email you're sending the wrong message.
Okay, back to football.