javamail 发送邮件报错：Could not connect to SMTP host: smtp.163.com, port: 25 ，问题解决

报错内容

Exception in thread "main" javax.mail.MessagingException: Could not connect to SMTP host: smtp.163.com, port: 465, response: -1
at com.sun.mail.smtp.SMTPTransport.openServer(SMTPTransport.java:1949)
at com.sun.mail.smtp.SMTPTransport.protocolConnect(SMTPTransport.java:654)
at javax.mail.Service.connect(Service.java:317)
at javax.mail.Service.connect(Service.java:176)
at javax.mail.Service.connect(Service.java:125)
at javax.mail.Transport.send0(Transport.java:194)
at javax.mail.Transport.send(Transport.java:124)

package com.liang.reggie.utils;

import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMessage.RecipientType;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Properties;

public class MailUtils {
    public static void main(String[] args) throws MessagingException {
        //可以在这里直接测试方法，填自己的邮箱即可
        sendTestMail("**8@qq.com", new MailUtils().achieveCode());
    }

    public static void sendTestMail(String email, String code) throws MessagingException {
        // 创建Properties 类用于记录邮箱的一些属性
        Properties props = new Properties();
        // 表示SMTP发送邮件，必须进行身份验证
        props.put("mail.smtp.auth", "true");
        //此处填写SMTP服务器
        props.put("mail.smtp.host", "smtp.163.com");
        //端口号，163邮箱服务器地址端口465
        props.put("mail.smtp.port", "465");
        // 此处填写，写信人的账号
        props.put("mail.user", "**@163.com");
        // 此处填写16位STMP口令
        props.put("mail.password", "**");
        props.put("mail.smtp.ssl.enable", true);
        // 构建授权信息，用于进行SMTP进行身份验证
        Authenticator authenticator = new Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                // 用户名、密码
                String userName = props.getProperty("mail.user");
                String password = props.getProperty("mail.password");
                return new PasswordAuthentication(userName, password);
            }
        };
        // 使用环境属性和授权信息，创建邮件会话
        Session mailSession = Session.getInstance(props, authenticator);
        // 创建邮件消息
        MimeMessage message = new MimeMessage(mailSession);
        // 设置发件人
        InternetAddress form = new InternetAddress(props.getProperty("mail.user"));
        message.setFrom(form);
        // 设置收件人的邮箱
        InternetAddress to = new InternetAddress(email);
        message.setRecipient(RecipientType.TO, to);
        // 设置邮件标题
        message.setSubject("Kyle's Blog 邮件测试");
        // 设置邮件的内容体
        message.setContent("尊敬的用户:你好!\n注册验证码为:" + code + "(有效期为一分钟,请勿告知他人)", "text/html;charset=UTF-8");
        // 最后当然就是发送邮件啦
        Transport.send(message);
        }

    public static String achieveCode() {  //由于数字 1 、 0 和字母 O 、l 有时分不清楚，所以，没有数字 1 、 0
        String[] beforeShuffle = new String[]{"2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F",
                "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "a",
                "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v",
                "w", "x", "y", "z"};
        List<String> list = Arrays.asList(beforeShuffle);//将数组转换为集合
        Collections.shuffle(list);  //打乱集合顺序
        StringBuilder sb = new StringBuilder();
        for (String s : list) {
            sb.append(s); //将集合转化为字符串
        }
        return sb.substring(3, 8);
    }
}

其实代码没啥问题，主要就是两个步骤

第一个，增加

props.put("mail.smtp.ssl.enable", true); 

如果没有这个代码块，那就请加上这个，因为这个是启用SMTP服务器的SSL加密连接。
网上到这就好了，但是我的代码还是报错，所以又有了第二步

第二步

打开目录
C:\Program Files\Java\jdk-17.0.5\conf\security

修改java.security：不要SSL3,TLSv1, TLSv1.1

dk.tls.disabledAlgorithms=MD5, SSLv3, DSA, RSA keySize < 2048
jdk.tls.disabledAlgorithms=RC4, DES, MD5withRSA, \
    DH keySize < 1024, EC keySize < 224, 3DES_EDE_CBC, anon, NULL, \
    include jdk.disabled.namedCurves

原文地址：https://blog.csdn.net/missgrass/article/details/135448111

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