ssl.SSLError: [SSL: WRONG

使用flask发送邮件的时候，报ssl.SSLError: [SSL: WRONG_VERSION_NUMBER] wrong version number (_ssl.c:1129)错误；
且浏览器返回：Internal Server Error
The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application.

解决办法：
将 MAIL_USE_SSL 设置为False。