javax.mail.MessagingException: Could not connect to SMTP host: smtp.qq.com, port: 465,

感觉其他都正确的话，如果自己电脑是winodws系统，查看一下hosts文件，因为可能里面多了一行 127.0.0.0 smtp.qq.com，

把它删除了，

javax.mail.MessagingException: Could not connect to SMTP host: localhost, port: 465;

如果是这个错误，

props.put("mail.smtp.host", "localhost");

上面的那行代码是错的，如果发邮件的人使用的是163邮箱，应该是props.put("mail.smtp.host", "smtp.163.com");

如果发件人使用的腾讯qq邮箱则应该是props.put("mail.smtp.host", "smtp.qq.com");

如果已经发送成功几封邮件，然后又报如下错误

javax.mail.MessagingException: Could not connect to SMTP host: smtp.exmail.qq.com, port: 25;timeout

可以参照

https://blog.csdn.net/ljj_9/article/details/52212469?ops_request_misc=%25257B%252522request%25255Fid%252522%25253A%252522160708064319725271067177%252522%25252C%252522scm%252522%25253A%25252220140713.130102334..%252522%25257D&request_id=160708064319725271067177&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~baidu_landing_v2~default-1-52212469.pc_search_result_no_baidu_js&utm_term=javax.mail.MessagingException:%20Could%20not%20connect%20to%20SMTP%20host:%20smtp.qq.com,%20port:%20465;

这篇博客进行修改

如果再次出现这样的错误

javax.mail.MessagingException: Could not connect to SMTP host: smtp.qq.com, port: 465;
  nested exception is:
    java.net.ConnectException: Connection timed out: connect

休息五分钟，再发邮件