Markdown Here is a Google Chrome, Firefox, and Thunderbird extension that lets you write email in Markdown and render them before sending. It also supports syntax highlighting (just specify the language in a fenced code block).
Writing email with code in it is pretty tedious. Writing Markdown with code in it is easy. I found myself writing email in Markdown in the Github in-browser editor, then copying the preview into email. This is a pretty absurd workflow, so I decided create a tool to write and render Markdown right in the email.