<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-mail</artifactId>
        </dependency>

mail:
    host: smtp.qq.com
    port: 587
    username: 写qq邮箱
    password: 在qq邮箱设置>账户>开启POP3/SMTP服务时获得
    default-encoding: UTF-8
    properties:
      smtp:
        socketFactoryClass: javax.net.ssl.SSLSocketFactory
      debug: true

 /**
     * 发送邮件
     * @param email 邮箱
     * @param session session会话
     * @return boolean
     */
    boolean sendMail(String email, HttpSession session);

 @Autowired
    protected SendMail sendMail;
 @Override
    public boolean sendMail(String email, HttpSession session) {
        String code = sendMail.sendSimpleMail(email);
        session.setAttribute("code",code);
        System.out.println(code);
        QueryWrapper<UserBean> wrapper = new QueryWrapper<>();
        wrapper.inSql("id","select id from tab_member where member_mail= "+"\""+email+"\"");
        UserBean user = userMapper.selectOne(wrapper);
        session.setAttribute("password",user.getMemberPassword());
        return code != null;
    }

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.mail.SimpleMailMessage;
import org.springframework.mail.javamail.JavaMailSender;
import org.springframework.stereotype.Component;
import java.util.Date;
import java.util.Random;
/**
 * @Author: Ljx
 * @Date: 2021/5/22 9:24
 */
@Component
public class SendMail {
    @Autowired
    JavaMailSender javaMailSender;
    int max = 99999;
    int min = 10000;
    Random random = new Random();
    public String sendSimpleMail(String email){
        int s = random.nextInt(max-min+1) + min;
        String code = String.valueOf(s);
        SimpleMailMessage message = new SimpleMailMessage();
        message.setSubject("找回密码");
        message.setFrom("写qq邮箱");
        message.setTo(email);
        message.setSentDate(new Date());
        message.setText("你的验证码是："+code);
        javaMailSender.send(message);
        return code;
    }
}

 @PostMapping("/sendEmail")
    @ApiOperation(value = "发送验证码", notes = "邮箱不能为空", httpMethod = "POST")
    @ApiImplicitParams({
            @ApiImplicitParam(paramType = "query", name = "email",
                    value = "邮箱", required = true, dataType = "String"),
    })
    public RespBean sendEmail(String email, HttpSession session){
        boolean judgment = iUserService.sendMail(email,session);
        if (judgment){
            String returnCode = (String) session.getAttribute("code");
            logger.info("发送验证码成功");
            return RespBean.ok("发送验证码成功",returnCode);
        }else{
            logger.error("发送验证码失败");
            return RespBean.error("发送验证码失败");
        }
    }