class Kramdown::Converter::Html

def convert_a(el, indent)
  res = inner(el, indent)
  attr = el.attr.dup
  if attr['href'].start_with?('mailto:')
    mail_addr = attr['href'][7..-1]
    attr['href'] = obfuscate('mailto') << ":" << obfuscate(mail_addr)
    res = obfuscate(res) if res == mail_addr
  end
  format_as_span_html(el.type, attr, res)
end