javax.mail.sendfailedexception:发送失败；嵌套异常为:发送时的类javax.mail.authenticationfailedexception

import javax.mail.*;
import javax.mail.internet.*;
import java.util.Properties;

public class EmailSender {
    public static void main(String[] args) {
        String to = "recipient@example.com";
        String from = "sender@example.com";
        String host = "smtp.example.com";
        String username = "your_username";
        String password = "your_password";

        Properties props = new Properties();
        props.put("mail.smtp.host", host);
        props.put("mail.smtp.port", "587");
        props.put("mail.smtp.starttls.enable", "true");
        props.put("mail.smtp.auth", "true");

        Session session = Session.getInstance(props, new Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(username, password);
            }
        });

        try {
            Message message = new MimeMessage(session);
            message.setFrom(new InternetAddress(from));
            message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(to));
            message.setSubject("Test Email");
            message.setText("This is a test email.");

            Transport.send(message);
            System.out.println("Email sent successfully.");
        } catch (MessagingException e) {
            e.printStackTrace();
        }
    }
}