How to Convert HTML to an OFT. Microsoft helps business users of its Office suite of programs to save time by allowing documents to be turned into reusable templates.

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.

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.