how can recognize whether the user sent the maild is id correct or not?

I am sending mail from .net application, my mail code is working fine but I dont want to allow the incorrect mail id's. So how can I recognize whether the user who sent the mail has the correct id or not开发者_JAVA技巧.

And i want to know the response of the mail which has been sent by the smtpclient.

    Configuration config = System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration(HttpContext.Current.Request.ApplicationPath);
    MailSettingsSectionGroup settings = (MailSettingsSectionGroup)config.GetSectionGroup("system.net/mailSettings");
     smtpHost = settings.Smtp.Network.Host;
     smtpport = settings.Smtp.Network.Port.ToString();
     smtpuser = settings.Smtp.Network.UserName;
     smtppwd = settings.Smtp.Network.Password;

    string MessageBody = string.Empty;
    try
    {

        message = new MailMessage();
        message.From = new MailAddress(smtpuser);

        message.To.Add(toMailAddress);

        message.BodyEncoding = System.Text.Encoding.UTF8;

        message.Subject = mailSubject;
        message.Body = mailMessage.ToString();



        message.IsBodyHtml = true;

        client = new SmtpClient();
        client.Host = smtpHost;
        //if (isSSLEnabled)
        //{
        //    client.EnableSsl = true;
        //}

        client.Port =  Convert.ToInt32(smtpport);
        client.EnableSsl = false;
        client.Credentials = new System.Net.NetworkCredential(smtpuser, smtppwd);

        client.Send(message);

    }
    catch (Exception ex)
    {
        string x = ex.Message;
    } 

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I would use a regular expression to validate the email.

http://www.codeproject.com/KB/recipes/EmailRegexValidator.aspx

As for the capturing the smtp response, this link should help you out greatly. Just check out the response section, its obvious you know the introduction items.

http://www.csharphelp.com/2007/01/howto-smtp-in-c/