MarkdownPad is a free Markdown editor for Windows that that can convert Text to HTML or XHTML for you easily. Dwnload the free version here.

They follow up with tips on turning some or all emails to plain text. If you're generally emailing inside a closed circle with Outlook users, HTML-formatted emails are probably fine.

Convert your scribbles to text with Google’s Handwriting Input app Your email has been sent Google's Handwriting Input app makes writing on your Android device easier than ever. Andy Wolber ...