decode (RMail::Message)

    # File rmail/message.rb, line 73
        def decode
          raise TypeError, "Can not decode a multipart message." if multipart?
          case header.fetch('content-transfer-encoding', '7bit').strip.downcase
          when 'quoted-printable'
            Utils.quoted_printable_decode(@body)
          when 'base64'
            Utils.base64_decode(@body)
          else
            @body
          end
        end