無法連接到SMTP主機：xxxx，端口：java中的25

Question

我無法使用Java發送電子郵件，它引發異常：無法連接到SMTP主機：xxxx，端口：25。

我使用telnet xxxx 25，然后以相同主機，端口，用戶和密碼的php代碼成功發送了電子郵件，因此我不認為由於網絡或防火牆問題而導致此問題。

在測試中，我使用gmail服務器（smtp.gmail.com：465）在Java中以電子郵件發送了OK，但未通過主機：xxxx端口25發送電子郵件。

這是我的Java代碼：HOST = xxxx

Properties mailServerProperties = System.getProperties();
mailServerProperties.put("mail.smtp.user", USER);
mailServerProperties.put("mail.smtp.host", HOST);
mailServerProperties.put("mail.smtp.port", 25);
mailServerProperties.put("mail.smtp.debug", "true");
mailServerProperties.put("mail.smtp.auth", "true");
mailServerProperties.put("mail.smtp.starttls.enable", "true");
mailServerProperties.put("mail.smtp.socketFactory.port", 25);
mailServerProperties.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");

javax.mail.Session getMailSession = javax.mail.Session.getDefaultInstance(mailServerProperties);
MimeMessage generateMailMessage = new MimeMessage(getMailSession);
generateMailMessage.setHeader("Content-Type", "text/plain; charset=UTF-8");
generateMailMessage.setSubject(subject, "UTF-8");
generateMailMessage.setFrom(new InternetAddress(ApiConstant.EMAIL, fromEmail, "UTF-8"));
generateMailMessage.addRecipients(Message.RecipientType.TO, toAddress);
generateMailMessage.addRecipients(Message.RecipientType.CC, ccAddress);
generateMailMessage.addRecipients(Message.RecipientType.BCC, bccAddress);

Multipart multipart = new MimeMultipart();
MimeBodyPart messagePart = new MimeBodyPart();
messagePart.setContent(content, "text/html; charset=UTF-8");
multipart.addBodyPart(messagePart);       
generateMailMessage.setContent(multipart);

logger.debug("Create transport");
Transport transport = getMailSession.getTransport("smtp");
transport.connect(HOST, 25, USER, PASS);
transport.sendMessage(generateMailMessage, generateMailMessage.getAllRecipients());
transport.close();

這是我的php代碼，它起作用了。

$mail = new PHPMailer();
$mail->Host = 'x.x.x.x';
$mail->Port = '25';
$mail->SMTPAuth = true;
$mail->Username = USER;
$mail->Password = PASS;
$mail->From = '.....';
$mail->FromName = '.....';

$mail->setLanguage('vi');
$mail->isHTML(true);
$mail->CharSet = 'UTF-8';
$mail->addAttachment(FILE_NAME);
$mail->addAddress('....');
$mail->Subject ="test";
$mail->Body = "test";
$mail->Body = $body;

請幫我。

Answer 1

在某些網絡上，IPv6可能會出現問題。 嘗試使用VM選項運行您的應用

-Djava.net.preferIPv4Stack=true

即

java -Djava.net.preferIPv4Stack=true -cp . MyClass