<!--<br/ /><br/ />Code highlighting produced by Actipro CodeHighlighter (freeware)<br/ />http://www.CodeHighlighter.com/<br/ /><br/ />-->private void SendMailByNet()
{
    MailMessage objMailMessage = new MailMessage();

objMailMessage.From = new MailAddress("UserFromMail");
    objMailMessage.To.Add(new MailAddress("UserToMail"));
    objMailMessage.BodyEncoding = System.Text.Encoding.UTF8;
    objMailMessage.Subject = "This is test";
    objMailMessage.Body = "Hi,Pippo<br/><br/> This is testing Email.";
    objMailMessage.IsBodyHtml = true;

SmtpClient objSmtpClient = new SmtpClient();
    objSmtpClient.Host = "SMTP";
    objSmtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;
    objSmtpClient.Credentials = new System.Net.NetworkCredential("UserFromMail", "PWD");
    //objSmtpClient.EnableSsl = true;//SMTP 服务器要求安全连接需要设置此属性

try
    {
        objSmtpClient.Send(objMailMessage);
    }
    catch (Exception ex)
    {
        Response.Write(ex.Message);
    }
}

<!--<br/ /><br/ />Code highlighting produced by Actipro CodeHighlighter (freeware)<br/ />http://www.CodeHighlighter.com/<br/ /><br/ />-->private void SendMailByWeb()
{
    MailMessage objMailMessage = new MailMessage();

SmtpMail.SmtpServer = System.Configuration.ConfigurationManager.AppSettings["SMTP"];

objMailMessage.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate", "1");
    objMailMessage.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendusername", System.Configuration.ConfigurationManager.AppSettings["FROM"]);
    //objMailMessage.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendpassword", System.Configuration.ConfigurationManager.AppSettings["PWD"]);//密码可以不提供
    objMailMessage.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpusessl", "true");//SMTP 服务器要求安全连接需要设置此属性

objMailMessage.BodyEncoding = System.Text.Encoding.UTF8;
    objMailMessage.From = System.Configuration.ConfigurationManager.AppSettings["FROM"];
    objMailMessage.To = "UserToMail";
    objMailMessage.Subject = "this is test";
    objMailMessage.Body = "Hi Pippo,<br/>This is testing EMAIL.";
    objMailMessage.BodyFormat = MailFormat.Html;

try
    {
        SmtpMail.Send(objMailMessage);
    }
    catch (Exception ex)
    {
        Response.Write(ex.Message);
    }