SpringBoot通过Jakarta SMTP跨IP发邮件遇Could not convert socket to TLS错误

我编写了一个MailMessageService类，在同一服务器使用localhost发送邮件时一切正常，但从其他IP发送、将SMTP主机设置为172.105.90.58时，出现了以下错误：

代码实现 #

@Service
@Slf4j
@Transactional(readOnly = true)
public class MailMessageService extends SimpleMailMessage {

    static Properties prop = new Properties();

    public MailMessageService() {
        super();
    }


    public void sendMessage(String subject, String body, String mailTo, String pathToFile) throws MessagingException, IOException {


        log.info("Sending email to: *{}* ", mailTo);

        Session session = Session.getInstance(prop, new Authenticator() {
            @Override
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication("info", "oT2ct2UUii87");
            }

        });


        Message message = new MimeMessage(session);
        message.setFrom(new InternetAddress("info@taradell.com.com"));

        message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(mailTo));
        message.setSubject(subject);

        MimeBodyPart mimeBodyPart = new MimeBodyPart();
        mimeBodyPart.setContent(body, "text/html; charset=utf-8");

        Multipart multipart = new MimeMultipart();
        multipart.addBodyPart(mimeBodyPart);

        log.info("pathToFile: *{}* ", pathToFile);

        if (pathToFile != null) {
            MimeBodyPart attachment = new MimeBodyPart();
            attachment.attachFile(pathToFile);
            multipart.addBodyPart(attachment);
        }

        log.info("Setting content");

        message.setContent(multipart);

        log.info("Sending message {} ", message);

        Transport.send(message);


    }


    public void sendMessage(String subject, String body, String mailTo) throws MessagingException, IOException {

        sendMessage(subject, body, mailTo, null);

    }


    @PostConstruct
    public void initProperties() {
        prop.put("mail.smtp.auth", true);
        prop.put("mail.smtp.starttls.enable", "true");
        prop.put("mail.smtp.host", "172.105.90.58");
        prop.put("mail.smtp.port", "25");
        prop.put("mail.smtp.ssl.trust", "172.105.90.58");
    }
}

错误信息 #

jakarta.mail.MessagingException: Could not convert socket to TLS
    at org.eclipse.angus.mail.smtp.SMTPTransport.startTLS(SMTPTransport.java:2173)
    at org.eclipse.angus.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:741)
    at jakarta.mail.Service.connect(Service.java:367)
    at jakarta.mail.Service.connect(Service.java:225)
    at jakarta.mail.Service.connect(Service.java:174)
    at jakarta.mail.Transport.send0(Transport.java:232)
    at jakarta.mail.Transport.send(Transport.java:102)

解决方案 #

• 检查端口与TLS模式匹配
  25端口通常用于非加密或STARTTLS升级，但部分服务器可能在该端口禁用了TLS。可以尝试：

  • 切换到标准TLS端口587，修改配置：prop.put("mail.smtp.port", "587")
  • 若服务器支持SSL直连，改用465端口并调整配置：

    prop.put("mail.smtp.ssl.enable", "true");
    prop.put("mail.smtp.port", "465");
    // 移除mail.smtp.starttls.enable配置
    

• 验证网络与防火墙规则

  • 用telnet 172.105.90.58 587或nc -zv 172.105.90.58 587测试发送端到SMTP服务器目标端口的连通性
  • 确认SMTP服务器的防火墙允许发送端IP的访问请求

• 强制指定兼容的TLS版本
  若JVM默认TLS版本与服务器不兼容，可强制指定支持的版本：

  prop.put("mail.smtp.starttls.required", "true");
  prop.put("mail.smtp.ssl.protocols", "TLSv1.2 TLSv1.3");
  

• 调整证书信任策略
  如果SMTP服务器用的是自签名证书，可临时跳过身份验证（仅测试用，生产环境不推荐）：

  prop.put("mail.smtp.ssl.checkserveridentity", "false");
  

  生产环境建议将服务器证书导入JVM的cacerts信任存储。

• 修复静态属性的潜在问题
  静态prop可能导致多实例下的配置混乱，建议改为非静态，或用@Value注入配置：

  @Value("${mail.smtp.host}")
  private String smtpHost;
  @Value("${mail.smtp.port}")
  private String smtpPort;
  
  @PostConstruct
  public void initProperties() {
      Properties prop = new Properties();
      prop.put("mail.smtp.auth", true);
      prop.put("mail.smtp.starttls.enable", "true");
      prop.put("mail.smtp.host", smtpHost);
      prop.put("mail.smtp.port", smtpPort);
      prop.put("mail.smtp.ssl.trust", smtpHost);
  }
  

内容的提问来源于stack exchange，提问作者Nunyet Calçada