springboot发qq邮件偶尔报错是什么问题?

Question

Mail server connection failed; nested exception is javax.mail.MessagingException: Got bad greeting from SMTP host: smtp.qq.com, port: 587, response: [EOF]. Failed messages: javax.mail.MessagingException: Got bad greeting from SMTP host: smtp.qq.com, port: 587, response: [EOF]