发送电子邮件给多个联系人

Question

I have a function which gets a list of addresses and send the same email message to every contact in the list using google smtp. but I affraid my code is not very efficient because it sends several seperate mails. how do I add more contacts to the same client and send all of them at once?

here is my function:

protected void btn_click(object sender, EventArgs e, List<string> address_l, List<string> names)
    {
        for (int i = 0; i < address_l.Count; i++)
        {
            var fromAddress = new MailAddress("dvir.rez@gmail.com", "Dvir");
            var toAddress = new MailAddress(address_l[i], names[i]);

            const string fromPassword = "2.4.862.4.86";
            const string subject = "test";
            string body = "Test body";

            var smtp = new SmtpClient
            {
                Host = "smtp.gmail.com",
                Port = 587,
                EnableSsl = true,
                DeliveryMethod = SmtpDeliveryMethod.Network,
                UseDefaultCredentials = false,
                Credentials = new NetworkCredential(fromAddress.Address, fromPassword)
            };
            using (var message = new MailMessage(fromAddress, toAddress)
            {
                Subject = subject,
                Body = body
            })
            {
                smtp.Send(message);
            }
        }

    }

Answer 1

Use BCC to add "blind carbon copy" recipients - they'll receive a copy of the message, without seeing other BCC'ed email addresses.

for (int i = 0; i < address_l.Count; i++)
{
   message.Bcc.Add(new MailAddress(address_l[i], names[i]));
}