Exception in thread "main" javax.mail.MessagingException: Could not connect to SMTP host: smtp.163.com, port: 25;
  nested exception is:
	javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?
	at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:2212)
	at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:722)
	at javax.mail.Service.connect(Service.java:342)
	at javax.mail.Service.connect(Service.java:222)
	at javax.mail.Service.connect(Service.java:243)
	at com.ailpha.aithink.job.controller.email.EmailUtil.deliverWithMime(EmailUtil.java:68)
	at com.ailpha.aithink.job.controller.email.EmailUtil.main(EmailUtil.java:149)

The reason is that the following code is used when SSL is enabled

if (emailConfigModel.getEnSsl() == 0) {
            MailSSLSocketFactory sf = new MailSSLSocketFactory();
            sf.setTrustAllHosts(true);
            prop.put("mail.smtp.ssl.enable", "true");
            prop.put("mail.smtp.ssl.socketFactory", sf);
        }

After searching various data, it is found that the port used when using SSL is port 465, not port 25. If SSL is not used, the port is port 25