1 //发送按钮 2 private void btn_Send_Click(object sender, EventArgs e) 3 { 4     //创建MailMessage对象 5     MailAddress from = new MailAddress("ntsmtp@163.com"); 6     MailAddress to = new MailAddress("miaosha5s@sohu.com"); 7     MailMessage mailMessage = new MailMessage(from, to) ; 8     mailMessage.Subject="主题"; 9     mailMessage.Body="这是一封来自远方的邮件.";   10 11     Attachment attachment01 = new Attachment("E:\\01.jpg"); //附件12     Attachment attachment02 = new Attachment("E:\\02.mp3");13     mailMessage.Attachments.Add(attachment01);14     mailMessage.Attachments.Add(attachment02);15 16     //创建SmtpClient对象      邮箱服务器smtp.163.com17     SmtpClient smtpClient = new SmtpClient("smtp.163.com");  18     smtpClient.UseDefaultCredentials = true;19     smtpClient.Credentials =20     new NetworkCredential("邮箱账号", "登录密码");   //邮箱认证登录21     //smtpClient.Timeout = 5000;22     try23     {24     //使用异步发送,不会阻塞该线程25     smtpClient.SendCompleted += new //完成发送调用回调函数26     SendCompletedEventHandler(SendCompletedCallback); 27     smtpClient.SendAsync(mailMessage, mailMessage);   28     }29     catch(Exception ex)30     {31       mailMessage.Dispose();    //主动释放资源32       smtpClient.Dispose();33       MessageBox.Show("发送失败!  "+System.Environment.NewLine+34                    "错误信息:"+ ex.Message);35     }36    return;37 }    

 1 //异步发送邮件完成的回调函数 2 public static void SendCompletedCallback(object sender,       3                                     AsyncCompletedEventArgs e) 4 { 5    SmtpClient smtpClient = (SmtpClient)sender; 6    //MailMessage mailMessage = (MailMessage)e.UserState; 7    if (e.Cancelled) 8    { 9      MessageBox.Show("Send canceled.");10    }11    if (e.Error != null)      12    {13      MessageBox.Show("错误信息: "+e.Error.ToString() );14    }15    else16    {17      MessageBox.Show("Message Sent.");18      smtpClient.Dispose();19      //mailMessage.Dispose();20    }21 }