Gmail目前已经启用了POP3和SMTP服务，与其他邮箱不同的是Gmail提供的POP3和SMTP是使用安全套接字层SSL的，因此常规的JavaMail程序是无法收发邮件的，下面是使用JavaMail如何收取Gmail邮件以及发送邮件的代码：

1. 邮件收取

package lius.javamail.ssl;

import java.io.UnsupportedEncodingException;
import java.security.*;
import java.util.Properties;
import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeUtility;

/**
* 用于收取Gmail邮件
* @author Winter Lau
*/
public class GmailFetch {

public static void main(String argv[]) throws Exception {

Security.addProvider(new com.sun.net.ssl.internal.ssl.Provider());
final String SSL_FACTORY = "javax.net.ssl.SSLSocketFactory";

// Get a Properties object
Properties props = System.getProperties();
props.setProperty("mail.pop3.socketFactory.class", SSL_FACTORY);
props.setProperty("mail.pop3.socketFactory.fallback", "false");
props.setProperty("mail.pop3.port", "995");
props.setProperty("mail.pop3.socketFactory.port", "995");

//以下步骤跟一般的JavaMail操作相同
Session session = Session.getDefaultInstance(props,null);

//请将红色部分对应替换成你的邮箱帐号和密码
URLName urln = new URLName("pop3","pop.gmail.com",995,null,
"[邮箱帐号]", "[邮箱密码]");
Store store = session.getStore(urln);
Folder inbox = null;
try {
store.connect();
inbox = store.getFolder("INBOX");
inbox.open(Folder.READ_ONLY);
FetchProfile profile = new FetchProfile();
profile.add(FetchProfile.Item.ENVELOPE);
Message[] messages = inbox.getMessages();
inbox.fetch(messages, profile);
System.out.println("收件箱的邮件数：" + messages.length);
for (int i = 0; i < messages.length; i++) {
//邮件发送者
String from = decodeText(messages[i].getFrom()[0].toString());
InternetAddress ia = new InternetAddress(from);
System.out.println("FROM:" + ia.getPersonal()+(+ia.getAddress()+));
//邮件标题
System.out.println("TITLE:" + messages[i].getSubject());
//邮件大小
System.out.println("SIZE:" + messages[i].getSize());
//邮件发送时间
System.out.println("DATE:" + messages[i].getSentDate());
}
} finally {
try {
inbox.close(false);
} catch (Exception e) {}
try {
store.close();
} catch (Exception e) {}
}
}

protected static String decodeText(String text)
throws UnsupportedEncodingException {
if (text == null)
return null;
if (text.startsWith("=?GB") || text.startsWith("=?gb"))
text = MimeUtility.decodeText(text);
else
text = new String(text.getBytes("ISO8859_1"));
return text;
}

}

2. 发送邮件

package lius.javamail.ssl;

import java.security.Security;
import java.util.Date;
import java.util.Properties;

import javax.mail.Authenticator;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

/**
* 使用Gmail发送邮件
* @author Winter Lau
*/
public class GmailSender {

public static void main(String[] args) throws AddressException, MessagingException {
Security.addProvider(new com.sun.net.ssl.internal.ssl.Provider());
final String SSL_FACTORY = "javax.net.ssl.SSLSocketFactory";
// Get a Properties object
Properties props = System.getProperties();
props.setProperty("mail.smtp.host", "smtp.gmail.com");
props.setProperty("mail.smtp.socketFactory.class", SSL_FACTORY);
props.setProperty("mail.smtp.socketFactory.fallback", "false");
props.setProperty("mail.smtp.port", "465");
props.setProperty("mail.smtp.socketFactory.port", "465");
props.put("mail.smtp.auth", "true");
final String username = "[邮箱帐号]";
final String password = "[邮箱密码]";
Session session = Session.getDefaultInstance(props, new Authenticator(){
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(username, password);
}});

// -- Create a new message --
Message msg = new MimeMessage(session);

// -- Set the FROM and TO fields --
msg.setFrom(new InternetAddress(username + "@mo168.com"));
msg.setRecipients(Message.RecipientType.TO,
InternetAddress.parse("[收件人地址]",false));
msg.setSubject("Hello");
msg.setText("How are you");
msg.setSentDate(new Date());
Transport.send(msg);

System.out.println("Message sent.");
}
}