可以使用GMail发mail，据说G官方限制一天内同一封邮件最多发送到500个联系人。代码如下：

namespace ConsoleApplication9{    class Program    {        static void Main(string[] args)        {            var from = new MailAddress("asdf@112.com", "cary");             var to = new MailAddress("chenghui921@126.com", "toname");            var message = new MailMessage(from, to);            message.Subject = "The subject";            message.Body = "The message body";            message.IsBodyHtml = true;            var host = "smtp.gmail.com";            var client = new SmtpClient(host, 587);            client.EnableSsl = true;            client.Credentials = new NetworkCredential("<
    
     >", "<
     
      >");            client.Send(message);            Console.ReadLine();                }              }
     
    

}

本文转自生鱼片博客园博客，原文链接：http://www.cnblogs.com/carysun/archive/2009/11/12/sendmail-by-gmail.html，如需转载请自行联系原作者