1.添加Maven依賴

 <dependency>
  <groupId>javax.mail</groupId>
  <artifactId>mail</artifactId>
  <version>1.4</version>
</dependency>
<dependency>
  <groupId>javax.activation</groupId>
  <artifactId>activation</artifactId>
  <version>1.1</version>
</dependency>

2.創建email.properties，設置發郵件郵箱的用戶名密碼

email.username=
email.password=

3.添加EmailAuthenticator繼承Authenticator

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import javax.mail.Authenticator;
import javax.mail.PasswordAuthentication;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class EmailAuthenticator extends Authenticator {

    private String username;

    private String password;

    @Override
    protected PasswordAuthentication getPasswordAuthentication() {
        return new PasswordAuthentication(username, password);
    }
}

4.創建EmailUtil工具類

import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

import javax.mail.Message.RecipientType;
import javax.mail.MessagingException;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public abstract class EmailUtil {

    private static Session session = null;

    private static EmailAuthenticator authenticator = null;

    static {
        try {
            InputStream inputStream = EmailUtil.class.getResourceAsStream("/email.properties");
            Properties properties = new Properties();
            properties.load(inputStream);

            authenticator = new EmailAuthenticator();
            String username = properties.getProperty("email.username");
            authenticator.setUsername(username);

            String password = properties.getProperty("email.password");
            authenticator.setPassword(password);

            String smtpHostName = "smtp." + username.split("@")[1];
            properties.put("mail.smtp.auth", "true");
            properties.put("mail.smtp.host", smtpHostName);

            session = Session.getInstance(properties, authenticator);
            inputStream.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private EmailUtil() { }

    /**
     * 通用發郵件方法
     */
    private static void send(List<String> recipients, SimpleEmail email) throws MessagingException {
        final MimeMessage message = new MimeMessage(session);
        message.setFrom(new InternetAddress(authenticator.getUsername()));
        InternetAddress[] addresses = new InternetAddress[recipients.size()];
        for (int index = 0; index < recipients.size(); index ++) {
            addresses[index] = new InternetAddress(recipients.get(index));
        }
        message.setRecipients(RecipientType.TO, addresses);
        message.setSubject(email.getSubject());
        message.setContent(email.getContent(), "text/html;charset=utf-8");

        Transport.send(message);
    }

    /**
     * 發送郵件
     */
    public static void send(String recipient, SimpleEmail email) throws MessagingException {
        List<String> recipients = new ArrayList<String>();
        recipients.add(recipient);
        send(recipients, email);
    }

    /**
     * 群發郵件
     */
    public static void massSend(List<String> recipients, SimpleEmail email) throws MessagingException {
        send(recipients, email);
    }
}

5.測試

public static void main(String[] args) throws Exception {
    SimpleEmail simpleEmail = new SimpleEmail();
    simpleEmail.setSubject("今天你學習了么？");
    simpleEmail.setContent("今天你寫博客了么");

    List<String> recipients = new ArrayList<String>();
    recipients.add("2668659188@qq.com");

    massSend(recipients, simpleEmail);
}

代碼地址：https://gitee.com/jsjack_wang/JavaDemo