Java自定义SMTP客户端实现邮件发送：解决530认证错误与EHLO应用

outToServer.println("HELO naver.com");

import java.util.Base64;

public class AuthEncoder {
    public static void main(String[] args) {
        String username = "your_email@naver.com"; // 替换为你的邮箱地址
        String password = "your_password"; // 替换为你的邮箱密码

        // 构造认证字符串：\0username\0password
        String authString = "\0" + username + "\0" + password;

        // 使用Base64编码
        String encodedAuth = Base64.getEncoder().encodeToString(authString.getBytes());
        System.out.println("Encoded Auth String: " + encodedAuth);
    }
}

import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.SSLSocket;
import java.io.*;
import java.net.*;
import java.util.Base64; // 导入Base64类

class MailClientWithAuth { // 将类名从MailServer修改为MailClientWithAuth更符合其功能
    public static void MailSender(String username, String password) throws Exception {
        String Reply;
        String To = "recipient@example.com"; // 替换为实际收件人
        String From = username; // 发件人通常就是认证的用户名
        // 邮件内容应包含Subject和其他Header，并用空行与邮件正文分隔
        String Data = "Subject: Hello from Java Client\r\n" +
                      "From: " + From + "\r\n" +
                      "To: " + To + "\r\n" +
                      "\r\n" + // 空行分隔Header和Body
                      "Hello this is computer networking tutorial.";

        SSLSocketFactory sslsocketf = (SSLSocketFactory) SSLSocketFactory.getDefault();
        System.out.println("Connect Start");
        // 使用smtp.naver.com作为示例，端口465为SMTPS（SMTP over SSL/TLS）
        SSLSocket socket = (SSLSocket) sslsocketf.createSocket("smtp.naver.com", 465);
        System.out.println("Connect Success");

        BufferedReader inFromServer = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        PrintWriter outToServer = new PrintWriter(socket.getOutputStream(), true);

        // 1. 读取服务器欢迎消息
        Reply = inFromServer.readLine();
        if (Reply.startsWith("220"))
            System.out.println("Server Connect Success! " + Reply);
        else {
            System.out.println("Server Connect Fail: " + Reply);
            System.exit(0);
        }

        // 2. EHLO command - 替代HELO，获取服务器支持的扩展
        outToServer.println("EHLO naver.com"); // 使用你的域名或IP
        Reply = inFromServer.readLine();
        ReplyCheck(Reply, "250"); // 检查EHLO响应，通常是多行，但我们只检查首行状态码
        // 这里可以解析EHLO响应以确认AUTH支持，但为简洁起见，直接尝试AUTH PLAIN

        // 3. AUTH PLAIN command
        String authString = "\0" + username + "\0" + password;
        String encodedAuth = Base64.getEncoder().encodeToString(authString.getBytes());
        outToServer.println("AUTH PLAIN " + encodedAuth);
        Reply = inFromServer.readLine();
        ReplyCheck(Reply, "235"); // 认证成功通常返回235

        // 4. MAIL FROM command
        outToServer.println("MAIL FROM: <" + From + ">");
        Reply = inFromServer.readLine();
        ReplyCheck(Reply, "250");

        // 5. RCPT TO command
        outToServer.println("RCPT TO: <" + To + ">");
        Reply = inFromServer.readLine();
        ReplyCheck(Reply, "250");

        // 6. DATA command
        outToServer.println("DATA");
        Reply = inFromServer.readLine();
        ReplyCheck(Reply, "354"); // 服务器准备接收邮件内容
        outToServer.println(Data);
        outToServer.println("."); // 邮件内容结束标志
        Reply = inFromServer.readLine(); // 读取DATA命令后的响应
        ReplyCheck(Reply, "250"); // 检查邮件内容发送后的响应

        // 7. QUIT command
        outToServer.println("QUIT");
        Reply = inFromServer.readLine();
        ReplyCheck(Reply, "221");

        outToServer.close();
        inFromServer.close();
        socket.close();
    }

    public static void ReplyCheck(String Reply, String Status) throws Exception {
        System.out.println("Server Reply: " + Reply);
        if (!Reply.startsWith(Status))
            throw new Exception("Unexpected server reply: " + Reply);
    }

    public static void main(String args[]) {
        String myEmail = "your_email@naver.com"; // 替换为你的邮箱
        String myPassword = "your_password"; // 替换为你的邮箱密码

        try {
            MailClientWithAuth.MailSender(myEmail, myPassword);
            System.out.println("Send Mail Success!");
        } catch (Exception e) {
            System.out.println("Send Mail Fail");
            System.out.println(e.toString());
            e.printStackTrace(); // 打印完整的堆栈信息有助于调试
        }
    }
}