TMail extension to collect plain-text parts.rb

module TMail
  class Mail
    def plain_text_body
      gather_plain_text_parts(self).flatten
    end
    
  private
    def gather_plain_text_parts(part)
      returning [] do |message|
        message << part.body.strip if part.content_type == 'text/plain'
        part.parts.each { |p| message << gather_plain_text_parts(p) }
      end
    end
  end
end