# File lib/em/protocols/smtpserver.rb, line 358
      def process_auth_line(line)
        plain = line.unpack("m").first
        _,user,psw = plain.split("\000")
        if receive_plain_auth user,psw
          send_data "235 authentication ok\r\n"
          @state << :auth
        else
          send_data "535 invalid authentication\r\n"
        end
        @state.delete :auth_incomplete
      end