public static void CreateCopyMessage(string server)
    {
        MailAddress from = new MailAddress("[email protected]", "Ben Miller");
        MailAddress to = new MailAddress("[email protected]", "Jane Clayton");
        MailMessage message = new MailMessage(from, to);
        // message.Subject = "Using the SmtpClient class.";
        message.Subject = "Using the SmtpClient class.";
        message.Body = @"Using this feature, you can send an email message from an application very easily.";
        // Add a carbon copy recipient.
        MailAddress copy = new MailAddress("[email protected]");
        message.CC.Add(copy);
        SmtpClient client = new SmtpClient(server);
        // Include credentials if the server requires them.
        client.Credentials = CredentialCache.DefaultNetworkCredentials;
        Console.WriteLine("Sending an email message to {0} by using the SMTP host {1}.",
             to.Address, client.Host);

        try
        {
            client.Send(message);
        }
        catch (Exception ex)
        {
            Console.WriteLine("Exception caught in CreateCopyMessage(): {0}", 
                ex.ToString());
        }
    }

//引入命名空间
using System;
using System.Net;
using System.Net.Mail;

class MainClass
{
    public static void Main(string[] args)
    {
        SmtpClient client = new SmtpClient("mail.somecompany.com", 25);

        client.Credentials =new NetworkCredential("[email protected]", "password");

        using (MailMessage msg = new MailMessage())
        {
            msg.From = new MailAddress("[email protected]");
            msg.Subject = "HI";

            msg.Body = "A message";

            msg.Attachments.Add(new Attachment("c:\\test.txt", "text/plain"));
            msg.Attachments.Add(new Attachment("C:\\test.exe", "application/octet-stream"));

            msg.To.Add(new MailAddress("message to address"));
            client.Send(msg);
        }

    }
}