You'll need an outgoing SMTP server set up by your hosting company or some other provider. Not sure if gmail perhaps smtp outgoing relays.
using System.Net.Mail;
var smtpClient = new SmtpClient();
var message = new MailMessage();
smtpClient.Host = "your smtp mail server name goes here";
smtpClient.Port = 25;
message.From = new MailAddress("youremailaddressgoeshere", "John Smith");
message.To.Add(new MailAddress("to email address"));
message.Subject = "subject line goes here";
message.IsBodyHtml = true;
message.Body = "html of the email";
smtpClient.Timeout = 15000;
smtpClient.EnableSsl = false;
smtpClient.Send(message);