错误如下：
at com.sun.mail.smtp.SMTPTransport$Authenticator.authenticate(SMTPTransport.java:826) at com.sun.mail.smtp.SMTPTransport.authenticate(SMTPTransport.java:761) at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:685) at javax.mail.Service.connect(Service.java:317) at javax.mail.Service.connect(Service.java:176) at javax.mail.Service.connect(Service.java:125) at javax.mail.Transport.send0(Transport.java:194) at javax.mail.Transport.send(Transport.java:124) at com.ecnu.mail.JavaMailDemo.gmailSender(JavaMailDemo.java:60) at com.ecnu.mail.JavaMailDemo.main(JavaMailDemo.java:24)
通过查看gmail邮箱帮助：https://support.google.com/accounts/answer/6010255?authuser=1，需要开启“允许不够安全的应用”
开启后，可以通过gmail邮箱发送邮件到其他邮箱。
附上工具类供大家使用：
public class SendGmail { /* * gmail邮箱SSL方式 */ private static void gmailssl(Properties props) { final String SSL_FACTORY = "javax.net.ssl.SSLSocketFactory"; props.put("mail.debug", "true"); props.put("mail.smtp.host", "smtp.gmail.com"); props.put("mail.smtp.ssl.enable", "true"); props.put("mail.smtp.socketFactory.class", SSL_FACTORY); props.put("mail.smtp.port", "465"); props.put("mail.smtp.socketFactory.port", "465"); props.put("mail.smtp.auth", "true"); } //gmail邮箱的TLS方式 private static void gmailtls(Properties props) { props.put("mail.smtp.auth", "true"); props.put("mail.smtp.starttls.enable", "true"); props.put("mail.smtp.host", "smtp.gmail.com"); props.put("mail.smtp.port", "587"); } /* * 通过gmail邮箱发送邮件 */ public static void gmailSender(String email) { // Get a Properties object Properties props = new Properties(); //选择ssl方式 gmailssl(props); final String username = "";//gmail邮箱 final String password = "";//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 -- try { msg.setFrom(new InternetAddress(username)); msg.setRecipients(Message.RecipientType.TO, InternetAddress.parse(email)); msg.setSubject(""); msg.setText(""); msg.setSentDate(new Date()); Transport.send(msg); } catch (AddressException e) { e.printStackTrace(); } catch (MessagingException e) { e.printStackTrace(); } System.out.println("Message sent."); } }文章来源: Java - 谷歌邮箱发送邮件详解