C＃处理来自邮件服务器的TELNET响应 [英] C# handle TELNET response from mail server

问题描述

大家好，

我想编写一个应用程序来检测是否存在电子邮件。这里的步骤：

步骤1. telnet mta7.am0.yahoodns.net 25 //连接到雅虎邮件服务器

步骤2. EHLO hi //说helo

步骤3.邮件来自：< [e-mail]> //检查发件人

步骤4. rcpt：< [e-mail]> //检查接收器



但是我只得到了STEP 1的响应。错过了步骤2,3,4的响应。



我只在下面得到了这个回复（步骤1）：

Hi everyone,
I want to code a application to detect email exist or not. Steps here:
STEP 1. telnet mta7.am0.yahoodns.net 25 // connect to yahoo mail server
STEP 2. EHLO hi // say helo
STEP 3. mail from: <[e-mail]> // check sender
STEP 4. rcpt to: <[e-mail]> // check receiver

But I only got response of STEP 1. And missed response from STEP 2,3,4.

I only got this response below (step 1):

220 mta4051.mail.gq1.yahoo.com ESMTP ready

请给我一个解决方案。非常感谢！



我的尝试：



我的代码：

Please give me a solution. Many thanks!

What I have tried:

My code:

static void Main(string[] args)
        {
            TcpClient tcpClient;
            NetworkStream networkStream;
            StreamWriter streamWriter;

            tcpClient = new TcpClient("mta7.am0.yahoodns.net", 25);

            byte[] writeBuffer;
            byte[] readBuffer;
            using (networkStream = tcpClient.GetStream())
            {
                networkStream.Flush();

                writeBuffer = System.Text.Encoding.ASCII.GetBytes("EHLO hi" + Environment.NewLine);
                networkStream.Write(writeBuffer, 0, writeBuffer.Length);
                networkStream.Flush();

                writeBuffer = System.Text.Encoding.ASCII.GetBytes("mail from: <[e-mail]>" + Environment.NewLine);
                networkStream.Write(writeBuffer, 0, writeBuffer.Length);
                networkStream.Flush();

                writeBuffer = System.Text.Encoding.ASCII.GetBytes("rcpt to: <[e-mail]>" + Environment.NewLine);
                networkStream.Write(writeBuffer, 0, writeBuffer.Length);
                networkStream.Flush();

                string output = null;

                if (networkStream.CanRead)
                {
                    readBuffer = new byte[tcpClient.ReceiveBufferSize];
                    networkStream.Read(readBuffer, 0, tcpClient.ReceiveBufferSize);

                    output = System.Text.Encoding.ASCII.GetString(readBuffer).Trim();
                    Console.WriteLine(output);
                }
                Console.ReadLine();
            }
        }

推荐答案

不要浪费你的时间，除非这是练习，这些天大多数邮件服务器不会报告电子邮件地址无效。



其次，谷歌c＃tcpclient发送电子邮件smtp，你会找到如何做到这一点的例子，如理查德说你需要在处理响应后一次发送一个命令。



使用C＃通过SMTP发送邮件 [ ^ ]

Don't waste your time unless this is for practice, these days most mail servers will not report that an email address is invalid.

Secondly, google "c# tcpclient send email smtp" and you'll find examples on how to do this, as Richard said you need to send the commands one at a time after processing the response.

Sending Mail Using C# via SMTP[^]

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