通過 SMTP 協議發送帶附件的郵件示例

using System;
using System.Collections.Generic;
using System.Text;
using System.Net.Mail;
using System.Net.Mime;

namespace ConsoleApp
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                MailMessage mailMsg = new MailMessage();
                mailMsg.From = new MailAddress("控制臺創建的發信地址", "昵稱");
                mailMsg.Sender = new MailAddress("顯示的發信地址");
                mailMsg.To.Add(new MailAddress("目標地址"));
                //mailMsg.CC.Add("抄送人地址");
                //mailMsg.Bcc.Add("密送人地址");
                //可選，設置回信地址 
                mailMsg.ReplyToList.Add("***");
                // 郵件主題
                mailMsg.Subject = "郵件主題C#測試";
                // 郵件正文內容
                string text = "歡迎使用阿里云郵件推送";
                string html = @"歡迎使用<a href=""https://dm.console.aliyun.com"">郵件推送</a>";
                mailMsg.AlternateViews.Add(AlternateView.CreateAlternateViewFromString(text, null, MediaTypeNames.Text.Plain));
                mailMsg.AlternateViews.Add(AlternateView.CreateAlternateViewFromString(html, null, MediaTypeNames.Text.Html));

                // 添加附件
                string file = "D:\\1.txt";
                Attachment data = new Attachment(file, MediaTypeNames.Application.Octet);
                mailMsg.Attachments.Add(data);
                //郵件推送的SMTP地址和端口
                SmtpClient smtpClient = new SmtpClient("smtpdm.aliyun.com", 25);

                //C#官方文檔介紹說明不支持隱式TLS方式，即465端口，需要使用25或者80端口(ECS不支持25端口)，另外需增加一行 smtpClient.EnableSsl = true; 故使用SMTP加密方式需要修改如下：
                //SmtpClient smtpClient = new SmtpClient("smtpdm.aliyun.com", 80);
                //smtpClient.EnableSsl = true;

                // 使用SMTP用戶名和密碼進行驗證
                System.Net.NetworkCredential credentials = new System.Net.NetworkCredential("控制臺創建的發信地址", "控制臺設置的SMTP密碼");
                smtpClient.Credentials = credentials;
                smtpClient.Send(mailMsg);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
        }
   }

}