参考：https://www.cnblogs.com/jiafuwei/p/9512400.html
https://blog.csdn.net/qq_39455116/article/details/83865661
配置示例：
spring:
mail:
host: smtp.163.com
username: 1111111@163.com
password: aaaaaaaa
default-encoding: UTF-8
properties:
mail:
smtp:
auth: true
ssl:
trust: smtp.163.com
socketFactory:
class: ‘javax.net.ssl.SSLSocketFactory‘
port: 465
starttls:
enable: true
required: true
原文：https://www.cnblogs.com/javabg/p/11398950.html