find_preferred_part

# File railties/lib/rails/mailers_controller.rb, line 56
    def find_preferred_part(*formats)
      if @email.multipart?
        formats.each do |format|
          return find_part(format) if @email.parts.any?{ |p| p.mime_type == format }
        end
      else
        @email
      end
    end