Java发送Gmail遇AuthenticationFailedException（无低安全应用选项）解决方案

我尝试用Java发送邮件，代码如下。已确认所有凭据正确，但仍抛出错误：javax.mail.AuthenticationFailedException: 535-5.7.8 Username and Password not accepted。之前常用的“开启低安全应用”选项已被谷歌禁用，请问该怎么解决？

import java.util.Properties;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class SendEmail {

    public static void main(String[] args) {

        // Recipient's email ID needs to be mentioned.
        String to = "sender@gmail.com";

        // Sender's email ID needs to be mentioned
        String from = "receiver@gmail.com";

        // Assuming you are sending email from through gmails smtp
        String host = "smtp.gmail.com";

        // Get system properties
        Properties properties = System.getProperties();

        // Setup mail server
        properties.put("mail.smtp.host", host);
        properties.put("mail.smtp.port", "465");
        properties.put("mail.smtp.ssl.enable", "true");
        properties.put("mail.smtp.auth", "true");
        properties.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");

        // Get the Session object.// and pass username and password
        Session session = Session.getInstance(properties, new javax.mail.Authenticator() {

            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication("receiver@gmail.com", "password");

            }

        });

        // Used to debug SMTP issues
        session.setDebug(true);

        try {
            // Create a default MimeMessage object.
            MimeMessage message = new MimeMessage(session);

            // Set From: header field of the header.
            message.setFrom(new InternetAddress(from));

            // Set To: header field of the header.
            message.addRecipient(Message.RecipientType.TO, new InternetAddress(to));

            // Set Subject: header field
            message.setSubject("This is the Subject Line!");

            // Now set the actual message
            message.setText("This is actual message");

            System.out.println("sending...");
            // Send message
            Transport.send(message);
            System.out.println("Sent message successfully....");
        } catch (MessagingException mex) {
            mex.printStackTrace();
        }

    }

}

错误提示：javax.mail.AuthenticationFailedException: 535-5.7.8 Username and Password not accepted

解决方法 #

1. 启用两步验证并生成应用专用密码 #

谷歌已经禁用低安全应用权限，现在必须通过应用专用密码来登录SMTP服务，前提是你的谷歌账号已经开启两步验证：

• 登录谷歌账号，进入「安全」设置页面，找到并开启「两步验证」，按照提示完成绑定；
• 开启后，在同一页面找到「应用专用密码」选项，点击创建；
• 选择应用类型为「邮件」，设备类型选「其他」（比如输入“Java邮件客户端”），点击生成；
• 把生成的16位无空格密码替换代码里的原密码。

2. 修正代码中的邮箱配置错误 #

你的代码里有个明显的逻辑错误：发件人和收件人的邮箱赋值搞反了，同时PasswordAuthentication里的邮箱必须和发件人邮箱一致，修正后代码片段如下：

// 收件人邮箱
String to = "receiver@gmail.com";
// 发件人邮箱
String from = "sender@gmail.com";

// ...

protected PasswordAuthentication getPasswordAuthentication() {
    // 这里要填发件人邮箱和对应的应用专用密码
    return new PasswordAuthentication("sender@gmail.com", "生成的16位应用专用密码");
}

3. 简化SMTP配置（可选优化） #

JavaMail的新版本已经不需要手动指定mail.smtp.socketFactory.class，可以把这行配置删掉，简化后的配置如下：

properties.put("mail.smtp.host", host);
properties.put("mail.smtp.port", "465");
properties.put("mail.smtp.ssl.enable", "true");
properties.put("mail.smtp.auth", "true");

内容的提问来源于stack exchange，提问作者Suchith Kumar