邮件发送提示 无法从传输连接中读取数据: net_io_connectionclosed

Question

 

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Net.Mail;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApp1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            bool a = SendEmail();
        }

        public bool SendEmail()
        {

            try
            {
                string sjr = "";//收件人地址   
                string fjr = "";//发件人地址  
                string Hostdy = "";//SMTP服务器地址 
                string Portdy = "";//SMTP端口，QQ邮箱填写587 
                string sqm = ""; //授权码


                sjr = textBox1.Text.ToString();
                fjr = textBox2.Text.ToString();
                Hostdy = textBox3.Text.ToString();
                Portdy = textBox4.Text.ToString();
                sqm = textBox5.Text.ToString();

                MailMessage msg = new MailMessage();

                msg.To.Add(sjr);//收件人地址  

                msg.From = new MailAddress(fjr, "Edward");//发件人邮箱，名称 

                msg.Subject = "This is a test email from QQ";//邮件标题 
                msg.SubjectEncoding = Encoding.UTF8;//标题格式为UTF8 

                msg.Body = "this is body";//邮件内容 
                msg.BodyEncoding = Encoding.UTF8;//内容格式为UTF8 

                SmtpClient client = new SmtpClient();

                client.Host = Hostdy;//SMTP服务器地址 
                client.Port = int.Parse(Portdy);//SMTP端口，QQ邮箱填写587 

                client.EnableSsl = false;//启用SSL加密 
                                         //发件人邮箱账号，授权码(注意此处，是授权码你需要到qq邮箱里点设置开启Smtp服务，然后会提示你第三方登录时密码处填写授权码)
                client.Credentials = new System.Net.NetworkCredential(fjr, sqm);

                client.Send(msg);//发送邮件
            }
            catch (Exception ex)

            {

                WriteLog(ex);
                return false;
            }
            return true;
        }

        private void label1_Click(object sender, EventArgs e)
        {

        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }


        public static void WriteLog(Exception ex, string LogAddress = "")
        {
            //如果日志文件为空，则默认在Debug目录下新建 YYYY-mm-dd_Log.log文件
            if (LogAddress == "")
            {
                LogAddress = Environment.CurrentDirectory + '\\' +
                    DateTime.Now.Year + '-' +
                    DateTime.Now.Month + '-' +
                    DateTime.Now.Day + "_Log.log";
            }

            //把异常信息输出到文件
            StreamWriter sw = new StreamWriter(LogAddress, true);
            sw.WriteLine("当前时间：" + DateTime.Now.ToString());
            sw.WriteLine("异常信息：" + ex.Message);
            sw.WriteLine("异常对象：" + ex.Source);
            sw.WriteLine("调用堆栈：\n" + ex.StackTrace.Trim());
            sw.WriteLine("触发方法：" + ex.TargetSite);
            sw.WriteLine();
            sw.Close();
        }

   

    }
}

直接放代码和错误，

我这个代码是自己做的测试的，外网发外网，用QQ邮箱是没问题的，

但是在客户服务器上就是走不通，客户给的邮箱，在服务器上是能PING通的，

也开放了入站出站策略。

 

邮箱是企业自建的邮箱，据说是邮箱只有一个密码，没有授权码，客户之前的系统，都是用java搭建的，用此密码能发送成功

    if (mailInfo.isValidate()) {   
     
        authenticator = new MyAuthenticator(mailInfo.getUserName(),mailInfo.getPassword());   
      }  
      // 根据邮件会话属性和密码验证器构造一个发送邮件的session    
      Session sendMailSession = Session.getInstance(pro,authenticator);
  // 根据session创建一个邮件消息   
      Message mailMessage = new MimeMessage(sendMailSession);   
      // 创建邮件发送者地址   
      Address from = new InternetAddress(mailInfo.getFromAddress());   
      // 设置邮件消息的发送者   
      mailMessage.setFrom(from);   
      // 创建邮件的接收者地址，并设置到邮件消息中   
      Address to = new InternetAddress(mailInfo.getToAddress());   
      mailMessage.setRecipient(Message.RecipientType.TO,to);   
      // 设置邮件消息的主题   
      mailMessage.setSubject(mailInfo.getSubject());   
      // 设置邮件消息发送的时间   
      mailMessage.setSentDate(new Date());   
      // 设置邮件消息的主要内容   
      String mailContent = mailInfo.getContent();   
      mailMessage.setText(mailContent);   
      // 发送邮件   
      Transport.send(mailMessage);  

有没有其他的发送方式