附录：ListServer.java
/**
* 类ListServer提供基本的邮件列表服务功能:读取指定邮件帐号的所有新邮件,然后转发给
* 在emailListFile文件中指定的所有邮件帐号（订阅者）.emailListFile中的邮件帐号格式
* 为每一行一个邮件帐号.
*/
import java.util.*;
import java.io.*;

import javax.mail.*;
import javax.mail.internet.*;
import javax.activation.*;

public class Class1
{
private static final String INBOX = "INBOX", POP_MAIL="pop3", SMTP_MAIL="smtp";
private boolean debugOn = false;
private String _smtpHost = null,
_pop3Host = null,
_user = null,
_password = null,
_emailListFile = null,
_fromName = null;
private InternetAddress[] _toList = null;

//main():创建和启动ListServer实例
public static void main(String args[])
throws Exception
{
//检查输入参数
if (args.length < 6)
{
System.err.println("Usage: java ListServer SMTP服务器 POP3服务器 POP3帐号 POP3帐号密码 订阅者清单文件 检查周期(分钟) 发信人名称");
System.exit(1);
}

// 将命令行参数赋值给对应的变量
String smtpHost = args[0], //smtp服务器
pop3Host = args[1], //pop3服务器
user = args[2], //pop3邮件帐号
password = args[3], //pop3邮件帐号密码
emailListFile=args[4], //订阅者清单文件
fromName = null; //发信人名称

int checkPeriod = Integer.parseInt(args[5]); //新邮件检查周期

if (args.length > 6)
fromName = args[6];

// 创建ListServer实例，循环处理新邮件
ListServer ls = new ListServer();
ls.setDebug(false);
while (true)
{
ls.debugMsg("ListServer启动...");
ls.process(smtpHost, pop3Host, user, password, emailListFile, fromName);
ls.debugMsg("ListServer暂停 (休息 " + checkPeriod + " 分钟)");
Thread.sleep(checkPeriod*1000*60);
}
}


// process(): 检查新邮件，调用 processMsg() 处理单个邮件
public void process(String smtpHost, String pop3Host, String user, String password, String emailListFile, String fromName)
throws Exception
{
_smtpHost = smtpHost;
_pop3Host = pop3Host;
_user = user;
_password = password;
_emailListFile = emailListFile;
if (fromName != null)
_fromName = fromName;

// 将订阅者帐号读入 java.util.Vector
Vector vList = new Vector(10);
BufferedReader listFile = new BufferedReader(new FileReader(emailListFile));
String line = null;
while ((line = listFile.readLine()) != null)
{
vList.addElement(new InternetAddress(line));
}
listFile.close();

debugMsg("共计 " + vList.size() + " 个订阅者");

_toList = new InternetAddress[vList.size()];
vList.copyInto(_toList);
vList = null;

// 获得 Session 对象
Properties sysProperties = System.getProperties();
Session session = Session.getDefaultInstance(sysProperties, null);
session.setDebug(debugOn);

// 连接POP3邮件服务器
Store store = session.getStore(POP_MAIL);
store.connect(pop3Host, -1, _user, _password);

// 打开缺省文件夹
Folder folder = store.getDefaultFolder();
if (folder == null)
throw new NullPointerException("没有缺省邮件文件夹");
folder = folder.getFolder(INBOX);
if (folder == null)
throw new NullPointerException("无法打开文件夹: " + folder);
folder.open(Folder.READ_WRITE);

// 获得新邮件数
int totalMessages = folder.getMessageCount();
if (totalMessages == 0)
{
debugMsg(folder + " 没有新邮件");
folder.close(false);
store.close();
return;
}

// 获得所有新邮件的属性和标记
Message[] messages = folder.getMessages();
FetchProfile fp = new FetchProfile();
fp.add(FetchProfile.Item.ENVELOPE);
fp.add(FetchProfile.Item.FLAGS);
fp.add("X-Mailer");
folder.fetch(messages, fp);

// 处理每一个新邮件
for (int i = 0; i < messages.length; i++)
{
if (!messages[i].isSet(Flags.Flag.SEEN))
processMsg(smtpHost, messages[i]);
messages[i].setFlag(Flags.Flag.DELETED, true);
}

folder.close(true);
store.close();
}

// processMsg(): 分析单个新邮件并调用sendMsg()将它转发给所有订阅者
private void processMsg(String smtpHost, Message message)
throws Exception
{
String replyTo=_user, subject, xMailer, messageText;
Date sentDate;
int size;
Address[] a=null;

// 获得邮件头信息 (发件人,收件人,邮件主题,发送日期等.)
if ((a = message.getFrom()) != null)
replyTo = a[0].toString();

subject = message.getSubject();
sentDate = message.getSentDate();
size = message.getSize(); String[] hdrs = message.getHeader("X-Mailer");
if (hdrs != null)
xMailer = hdrs[0];

// 转发邮件
sendMsg(_user, sentDate, replyTo, subject, message);
}

// sendMsg():将指定邮件转发给所有订阅者
private void sendMsg(String from, Date sentDate, String replyTo,
String subject, Message message)
throws Exception
{
// 获得缺省 Session实例
Properties props = new Properties();
props.put("mail.smtp.host", _smtpHost);
Session session = Session.getDefaultInstance(props, null);

// 创建转发邮件,填写各栏目
Address replyToList[] = { new InternetAddress(replyTo) };
Message newMessage = new MimeMessage(session);
if (_fromName != null)
newMessage.setFrom(new InternetAddress(from,
_fromName + " / " + replyTo));
else
newMessage.setFrom(new InternetAddress(from));
newMessage.setReplyTo(replyToList);
newMessage.setRecipients(Message.RecipientType.BCC, _toList);
newMessage.setSubject(subject);
newMessage.setSentDate(sentDate);

// 填写转发邮件内容（注意区分内容类型）
Object content = message.getContent(); //原邮件内容
String debugText = "主题: " + subject + ", 发送日期: " + sentDate;
if (content instanceof Multipart)
{
debugMsg("发送复合内容邮件 (" + debugText + ")");
newMessage.setContent((Multipart)message.getContent());
}
else
{
debugMsg("发送纯文本邮件 (" + debugText + ")");
newMessage.setText((String)content);
}
// 转发邮件
Transport transport = session.getTransport(SMTP_MAIL);
transport.connect(_smtpHost, _user, _password);
transport.sendMessage(newMessage, _toList);
}

private void debugMsg(String s)
{
if (debugOn)
System.out.println(new Date() + "> " + s);
}

public void setDebug(boolean state) { debugOn = state; }