向Gmail发送邮件时出错

Question

  

可能重复：
  send mail to Gmail account

我使用套接字通过Gmail发送邮件，但我一次又一次地收到的错误是

530 5.7.0必须先发出STARTTLS命令

public class SMTPDemo {
   static InputStream inn;
    private static BufferedReader in;
    private static String subject;
    private static String message;

  public static void main(String args[]) throws IOException,
      UnknownHostException {
      subject="Pakistan";
      message="I am Alive";
    String from = "sharpzain@gmail.com";
    String to = "sharpzain@gmail.com";
    String mailHost = "smtp.gmail.com";
    Socket smtpPipe;
    smtpPipe = new Socket("smtp.gmail.com", 25);
    System.out.println(smtpPipe);
    OutputStream outt;
     outt = smtpPipe.getOutputStream();
     BufferedWriter wtr;
      inn = smtpPipe.getInputStream();
      in = new BufferedReader(new InputStreamReader(inn));
    wtr = new BufferedWriter(new OutputStreamWriter(outt));
    /*SMTP mail = new SMTP(mailHost);
    if (mail != null) {
      if (mail.send(new FileReader(msgFile), from, to)) {
        System.out.println("Mail sent.");
      } else {
        System.out.println("Connect to SMTP server failed!");
      }
    }
    System.out.println("Done.");*/
   say( wtr, "HELO kth.se" );
say( wtr, "MAIL FROM: <"+from+">" );
say( wtr, "RCPT TO: <" + to + ">" );
say(wtr,"data");
say(wtr,"subject: "+subject);
say(wtr,"From: "+from);
say(wtr,"To: "+to+"\r\n");
say(wtr,message+"  ");
say(wtr,"\r\n.");
say( wtr, "RSET" );
say( wtr, "QUIT" );
  }


static void say( BufferedWriter wr, String text )
throws IOException {
wr.write( text + "\r\n" );

String recipientOK = in.readLine();
System.out.println(text);
System.out.println(recipientOK);
wr.flush();
}

发送HELO和FROM时需要一个OK响应，但得到响应必须在RCPT和其他命令之后发出TTLS。任何人都可以告诉我它背后的问题是什么？