这里只做简单的接收解析邮件发送请求，后续会在这个基础上做深入探索。

发送组件：

/**
 * @author: Nemo
 * @date: 2018/9/28.
 */
public class MainSender {

    public static void send() {
        String sender = "sender@link-nemo.com";
        String receiver = "reciver@link-nemo.com";
        String password = "xxxxxx";
        String user = new BASE64Encoder().encode(sender.getBytes());
        String pass = new BASE64Encoder().encode(password.getBytes());
        try {
            //邮箱服务的地址，端口(smtp服务)
            Socket socket = new Socket("10.1.10.37", 8086);
            InputStream inputStream = socket.getInputStream();
            OutputStream outputStream = socket.getOutputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
            //
            PrintWriter writter = new PrintWriter(outputStream, true);
            System.out.println(reader.readLine());
            //Hello
            writter.println("HELO Nemo");
            System.out.println(reader.readLine());
            //AUTH LOGIN
            writter.println("auth login");
            System.out.println(reader.readLine());
            writter.println(user);
            System.out.println(reader.readLine());
            writter.println(pass);
            System.out.println(reader.readLine());
            //Above   Authentication successful

            //Set mail from   and   rcpt to
            writter.println("mail from:<" + sender + ">");
            System.out.println(reader.readLine());
            writter.println("rcpt to:<" + receiver + ">");
            System.out.println(reader.readLine());

            //Set data
            writter.println("data");
            System.out.println(reader.readLine());
            //title
            writter.println("subject:你好Nemo，这里是标题");
            writter.println("from:" + sender);
            writter.println("to:" + receiver);
            writter.println("Content-Type: text/plain;charset=\"utf-8\"");
            writter.println();
            //content
            writter.println("你好Nemo，这里是主体内容?");
            writter.println(".");
            writter.println("");
            System.out.println(reader.readLine());

            //Say GoodBye
            writter.println("rset");
            System.out.println(reader.readLine());
            writter.println("quit");
            System.out.println(reader.readLine());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String args[]){
        send();
    }

}

接收组件：

/**
 * @author: Nemo
 * @date: 2018/9/28.
 */
public class MainServerTest {

    /**
     * 入口主函数
     * @param args
     */
    public static void main(String[] args) {
        MainServerTest server = new MainServerTest();
        server.start();
    }

    /**
     * 启动服务器，并接收用户请求进行处理
     */
    private void  start() {
        ServerSocket serverSocket = null;
        try {
            //打开端口访问
            serverSocket = new ServerSocket(8086, 1, InetAddress.getByName("10.1.10.37"));
        } catch (UnknownHostException e) {
            e.printStackTrace();
            System.exit(-1);
        } catch (IOException e) {
            e.printStackTrace();
            System.exit(-1);
        }

        //开始处理请求
        dealRequest(serverSocket);
    }

    /**
     * 开始处理请求
     * @param serverSocket
     */
    private void dealRequest(ServerSocket serverSocket){
        while(true) {
            try {
                //创建socket,等待请求
                Socket socket = serverSocket.accept();
                //如果有请求，则直接放到线程中直接处理即可
                Thread thread = new Thread(new DealRequestThread(socket));
                thread.start();
            } catch (IOException e) {
                e.printStackTrace();
                //异常不终止所有进程，应立即继续下一个请求
                continue;
            }
        }
    }

}

class DealRequestThread implements Runnable{
    private Socket socket;

    public DealRequestThread(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        try {

            Thread current = Thread.currentThread();
            System.out.println("当前处理线程：" + current.getName());

            //本次请求的输入流
            InputStream input = socket.getInputStream();

            //对于本次请求的输出流
            OutputStream output = socket.getOutputStream();

            BufferedReader reader = new BufferedReader(new InputStreamReader(input));
            PrintWriter writter = new PrintWriter(output, true);

            //告诉对方会话开始
            writter.println("220 Hello there,this is Nemo mail.");

            //第一行，回应对方的打招呼
            String line = reader.readLine();
            System.out.println(line);
            writter.println("250 Copy that.");

            //第二行，对方开始请求验证登录，提示对方输入用户名
            line = reader.readLine();
            System.out.println(line);
            writter.println("334 Username:");

            //第三行，对方已输入用户名，提示对方输入密码
            line = reader.readLine();
            System.out.println(line);
            writter.println("334 Password:");

            //第四行，对方已输入密码，开始验证对方用户名密码是否成功
            line = reader.readLine();
            System.out.println(line);
            //TODO 校验
            writter.println("235 Authentication successful");

            //第五行，接收对方发送账号
            line = reader.readLine();
            System.out.println(line);
            writter.println("250 Mail Ok");

            //第六行，接收对方接收账号
            line = reader.readLine();
            System.out.println(line);
            writter.println("250 Rcpt Ok");

            //第七行，对方发送data标记主体内容开始，这里需要提示对方结束标记
            line = reader.readLine();
            System.out.println(line);
            writter.println("354 End data with .");

            //开始接受主体内容
            //TODO 把内容存到库中，准备下行投递发送
            while (!".".equals(line = reader.readLine())) {
                System.out.println("主体内容："+line);
            }
            reader.readLine();
            writter.println("250 Data Ok:queued as freedom");

            //结尾：
            line = reader.readLine();
            System.out.println(line);
            writter.println("250 Reset Ok");

            //结束会话
            line = reader.readLine();
            System.out.println(line);
            writter.println("250 Bye");

            socket.close();
        } catch (IOException e) {
            //错误只做异常堆栈输出，不向外抛出
            e.printStackTrace();
        }
    }
}