我的java程序卡在Transport.send（消息）行

Question

我有一个应用程序，用户请求报告并将其作为压缩的csv文件附件在她的收件箱中获取。 它适用于发送带有最大44kb的zip文件的电子邮件。但程序永远陷入困境 Transport.send（消息）;行，同时发送更大尺寸的报告。

我搜索类似问题并应用了超时解决方案，但它对我没有帮助。

    try {
        Properties props = mailProperties.asProperties();
        props.put("mail.smtp.connectiontimeout", TIMEOUT);
        props.put("mail.smtp.timeout", TIMEOUT);
        Session session = Session.getDefaultInstance(props, new javax.mail.Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(mailProperties.getUsername(), mailProperties.getPassword());
            }
        });
        session.setDebug(true);
        MimeMessage message = new MimeMessage(session);
        message.setFrom(new InternetAddress(mail.getFrom()));
        message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(mail.getTo()));
        message.setSubject(mail.getSubject());
        MimeBodyPart mbp1 = new MimeBodyPart();
        mbp1.setText(mail.getText());
        MimeBodyPart mbp2 = new MimeBodyPart();
        mbp2.attachFile(filePath);
        Multipart mp = new MimeMultipart();
        mp.addBodyPart(mbp1);
        mp.addBodyPart(mbp2);
        message.setContent(mp);
        Transport.send(message);  // get stuck here
    } catch (Exception e) {
        LOGGER.error("Error : ", e);
        throw new RuntimeException("Sending email failed.", e);
    }