Sending large emails using javax.mail, delivery failed for some emails

Question

I am sending large number of emails(around 1000) to the users using javax.mail from my SMTP server, which owns for my domain. And all the recipients are in the same domain email.

When sending mail, if there is only success then I am saving the token in userToken table. Else I am not saving the token in table. After completion of the process, userToken table inserted with 950 rows, which means there is success for all the emails.

I have written following code to sending bulk emails, But almost 300 emails were not received by the users. I din't get any errors while execution,

@RequestMapping(value = "bulkMail")
public  @ResponseBody  String bulkMail(Model model, HttpServletRequest request,@RequestParam(value="myArray") Long[] myArray, HttpServletResponse response) throws IOException {
    Session session = null;
    EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("roca");
    EntityManager entityManager = entityManagerFactory.createEntityManager();
    entityManager.getTransaction().begin();
    HttpSession httpSession = request.getSession(false);
    session = getRocaSession();
    Test test = (Test) httpSession.getAttribute("test");

    for (int i = 0; i < myArray.length; i++) {
        User user = entityManager.createQuery( "SELECT u FROM User u where u.userId=" + myArray[i], User.class).getSingleResult();

        UserToken userToken;
        try {
            userToken = entityManager.createQuery("SELECT ut FROM UserToken ut where ut.testId="+test.getId()+" and ut.userId="+myArray[i], UserToken.class).getSingleResult();
        } catch (Exception e) {
            userToken = new UserToken();
        }

        String mailStatus = sendMail(userToken,test,request, user.getUserId(),  user.getUserName(), context, user.getEmailId(),session);
        if (!mailStatus.equals("failure")) {
            userToken.setToken(mailStatus);
            userToken.setCreatedDate(new Date());
            userToken.setUpdatedDate(new Date());
            userToken.setTestId(test.getId());
            userToken.setUserId(user.getUserId());
            userToken.setUsed(0);
            testDao.saveOrUpdate(userToken);
        }
    }
    entityManager.getTransaction().commit();
    entityManager.close();
    return "Emails have been send to Users";
}

Sending emails

public String sendMail(UserTestToken userTestToken, Test test,HttpServletRequest request, Long accountId,String accountName,
        String context,String accountEmail,Session session) {
    String token = getToken();
    try {
        String email = mailService.sendAlert(test, accountEmail,"User Triger", "noreply@mydomain.com", "Val", accountId, token, context, accountName, session);
        if (!email.equals("failure")) {
            return token;
        }else {
            return "failure";
        }
    } catch (Exception e) {
        return "failure";
    }       
}

Getting session for the emails

public Session getSession() {
    Properties props = new Properties();
    props.put("mail.smtp.auth", "false");
    props.put("mail.smtp.host", "gatesmtp.moc.domain.com");
    props.put("mail.smtp.port", "25");
    Session session = Session.getInstance(props);
    session.setDebug(false);
    return session;
}

MailService Implementaion

public String sendTestMailAlert(Test test, String accountEmail, String receiverName, String senderEmail, String url, Long accountId, String token, String context, String       accountName, Session session)
{
    String subject = "Subject";
    String content = "Content";
    return sendMail(accountEmail, content, subject, receiverName, senderEmail, session);
}


private String sendMail(String receiverMailIds, String content, String subject, String employeeName, String employeeEmail, Session session) {
    try {
        Message message = new MimeMessage(session);
        try {
            message.setFrom(new InternetAddress(employeeEmail, employeeName));
        } catch (UnsupportedEncodingException e) {
            this.logger.error("Mail service address catch UnsupportedEncodingException");
        }
        message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(receiverMailIds));
        message.setSubject(subject);
        message.setContent(content, "text/html");
        Transport.send(message);
        return "success";
    } catch (Exception e) {
        this.logger.error("Mail Exception - " + receiverMailIds);
    }
    return "failure";
}

https://stackoverflow.com/questions/13287515/how-to-send-bulk-mails-using-javax-mail-api-efficiently-can-we-use-reuse-auth — Incredible, Aug 24 '17 at 07:42

score 0 · Accepted Answer · answered Aug 24 '17 at 15:50

Problem is not in your code: if mail is queued correctly in your mailserver, issue is on the SMTP server of final recipient.

When your SMTP server (who has to deliver message correctly enqueued) contacts recipient SMTP server, maybe (surely...) recipient SMTP rejects email for some reasons (spam? unknown user? too many messages? mailbox full?). So your SMTP server can't deliver the email, and tries to send it back to the sender (that you defined as "noreply@domain.com"). If this mailbox doesn't exist, your SMTP server deletes message and (normally) logs that action just on its internal logs. That's why you can't notice what's happened.

You can use for testing purposes a real sender address instead of the noreply one.

Have fun :)

Sending large emails using javax.mail, delivery failed for some emails

1 Answers1