do_start

# File lib/net/smtp.rb, line 388
    def do_start( helodomain, user, secret, authtype )
      raise IOError, 'SMTP session already started' if @started
      check_auth_args user, secret, authtype if user or secret

      @socket = InternetMessageIO.old_open(@address, @port,
                                       @open_timeout, @read_timeout,
                                       @debug_output)
      check_response(critical { recv_response() })
      begin
        if @esmtp
          ehlo helodomain
        else
          helo helodomain
        end
      rescue ProtocolError
        if @esmtp
          @esmtp = false
          @error_occured = false
          retry
        end
        raise
      end
      authenticate user, secret, authtype if user
      @started = true
    ensure
      @socket.close if not @started and @socket and not @socket.closed?
    end