代碼：

import java.util.Properties;

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

import org.apache.commons.lang3.StringUtils;


public class EmailUtil {

	/**
	 * 發送郵件
	 * @param to 接收郵件郵箱號
	 * @param cc 抄送郵件郵箱號
	 * @param subject 郵件標題
	 * @param content 郵件內容
	 * @return
	 */
	public boolean sendEmail(String to, String cc, String subject, String content) {
		if (StringUtils.isEmpty(to)) {
			return false;
		}
		EmailConfig config = createEmailConfig(to, cc);
		try {
			return send(config, subject, content);
		} catch (Exception e) {
			e.printStackTrace();
			return false;
		}
	}
	
	private static EmailConfig createEmailConfig(String to, String cc) {
		EmailConfig config = new EmailConfig();
		config.setHost("發送郵件服務器");
		config.setPort("服務器發送端口");
		config.setEmail("系統使用郵箱號");
		config.setUserName("系統發送郵件用戶名");
		config.setPassword("系統發送郵件所用郵箱密碼");
		config.setToEmails("接收郵件郵箱號");
		config.setCcEmails("抄送郵件郵箱號");
		return config;
	}
	
	private static boolean send(EmailConfig config, String subject, String content) {
		Session session = EmailUtil.creatSession(config);
		try {
			MimeMessage message = new MimeMessage(session);
			// 設置郵件頭及編碼格式
			subject = MimeUtility.encodeWord(subject, "UTF-8", "Q");
			message.setSubject(subject);
			// 郵件署名
			message.setFrom(new InternetAddress(config.getEmail(), config.getUserName()));
			// 消息接收者(收件地址)
			if (StringUtils.isNotBlank(config.getToEmails())) {
				String[] emails = config.getToEmails().split(",");
				InternetAddress[] addresses = new InternetAddress[emails.length];
				for (int i = 0; i < emails.length; i++) {
					addresses[i] = new InternetAddress(emails[i]);
				}
				message.addRecipients(Message.RecipientType.TO, addresses);
			}
			// 消息抄送者(收件地址)
			if (StringUtils.isNotBlank(config.getCcEmails())) {
				String[] emails = config.getCcEmails().split(",");
				InternetAddress[] addresses = new InternetAddress[emails.length];
				for (int i = 0; i < emails.length; i++) {
					addresses[i] = new InternetAddress(emails[i]);
				}
				message.addRecipients(Message.RecipientType.CC, addresses);
			}
			message.saveChanges();
			// 設置郵件內容及編碼格式
			// 後一個參數可以不指定編碼，如"text/plain"，但是將不能顯示中文字符
			message.setContent(content, "text/plain;charset=UTF-8");
			// 發送
			Transport.send(message);
		} catch (Exception e) {
			e.printStackTrace();
			return false;
		}
		return true;
	}
	
	private static Session creatSession(EmailConfig config) {
		Properties props = new Properties();
		props.setProperty("mail.transport.protocol", "SMTP");
		props.setProperty("mail.smtp.host", config.getHost());
		props.setProperty("mail.smtp.port", config.getPort());
		props.setProperty("mail.smtp.auth", "true");
		props.setProperty("mail.smtp.ssl.enable", "true");
		props.setProperty("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
		props.setProperty("mail.smtp.socketFactory.fallback", "false");
		props.setProperty("mail.smtp.socketFactory.port", config.getPort());
		props.setProperty("mail.smtp.connectiontimeout", "5000");
		Session session = Session.getInstance(props, new Authenticator() {
			@Override
			protected PasswordAuthentication getPasswordAuthentication() {
				// 登錄用戶名密碼
				return new PasswordAuthentication(config.getEmail(), config.getPassword());
			}
		});
		// session.setDebug(true);
		return session;
	}
}

Java實現發送郵件功能