import java.io.*;import java.net.*;//本程序實現郵件傳輸功能public class SMTPClient {    public static void main(String[] args) {        try {            if (args.length >= 1)		System.getProperties().put("mail.host", args[0]);	     BufferedReader in =new BufferedReader(new InputStreamReader(System.in));             System.out.print("From: ");            String from = in.readLine();            System.out.print("To: ");            String to = in.readLine();            System.out.print("Subject: ");            String subject = in.readLine();             URL u = new URL("mailto:" + to);                URLConnection c = u.openConnection();             c.setDoInput(false);                              c.setDoOutput(true);                              System.out.println("Connecting...");              System.out.flush();                              c.connect();                                     PrintWriter out =                                     new PrintWriter(new OutputStreamWriter(c.getOutputStream()));                     out.print("From: \"" + from + "\" <" +	        System.getProperty("user.name") + "@" + 	        InetAddress.getLocalHost().getHostName() + ">\n");            out.print("To: " + to + "\n");            out.print("Subject: " + subject + "\n");            out.print("\n");              System.out.println("Enter the message. " + 			       "End with a '.' on a line by itself.");                   String line;            for(;;) {                line = in.readLine();                if ((line == null) || line.equals(".")) break;                out.print(line + "\n");            }                   out.close();            System.out.println("Message sent.");        }        catch (Exception e) {              System.err.println(e);            System.err.println("Usage: java SMTPClient [<mailhost>]");        }    }}