Regular Expressions for Internet Mail
Use kramdown to convert the .md file to .xml, then use xml2rfc to convert .xml file into .html and .txt
kramdown-rfc2629 draft-seantek-mail-regexen.md > draft-seantek-mail-regexen.xml
xml2rfc draft-seantek-mail-regexen.xml --text --html`
Here are links that will directly convert the latest master branch: