报错信息如下：

java
org.springframework.mail.MailSendException: Mail server connection failed; nested exception is javax.mail.MessagingException: Could not connect to SMTP host: smtp.qq.com, port: 465, response: -1. Failed messages: javax.mail.MessagingException: Could not connect to SMTP host: smtp.qq.com, port: 465, response: -1

解决办法：

在 application.yml 中将邮件配置为 SSL 连接

yml

spring:
  mail:
    host: smtp.qq.com
    username: 你的邮箱账号
    password: 你的邮箱授权码(QQ邮箱)
    port: 465
    protocol: smtp
    default-encoding: utf-8
    properties:
      mail:
        smtp:
          auth: true
          starttls:
            enable: true
            required: true
          ssl:
            enable: true
          socketFactory:
            port: 465
            class: javax.net.ssl.SSLSocketFactory

如果你使用的是 properties 文件，应该修改为：

properties

# JavaMailSender 配置
spring.mail.host=smtp.qq.com
spring.mail.username=你的邮箱账号
spring.mail.password=你的邮箱授权码(QQ邮箱)
spring.mail.port=465
spring.mail.default-encoding=utf-8
spring.mail.properties.mail.smtp.auth=true
spring.mail.properties.mail.smtp.starttls.enable=true
spring.mail.properties.mail.smtp.starttls.required=true
# SSL 配置
spring.mail.protocol=smtp
spring.mail.properties.mail.smtp.ssl.enable=true
spring.mail.properties.mail.smtp.socketFactory.port=465
spring.mail.properties.mail.smtp.socketFactory.class=javax.net.ssl.SSLSocketFactory

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来源：https://www.cnblogs.com/songjilong/p/12577010.html