If it is working on local and now on server, then there may not be code issue, you need to check other things like firewall settings.
What error you got exactly ?
try out with port number 587, see below snippet
MailMessage mail = new MailMessage();
mail.Subject = "Your Subject";
mail.From = new MailAddress("senderMailAddress");
mail.To.Add("ReceiverMailAddress");
mail.Body = "Hello! your mail content goes here...";
mail.IsBodyHtml = true;
SmtpClient smtp = new SmtpClient("smtp.gmail.com", 587);
smtp.EnableSsl = true;
NetworkCredential netCre = new NetworkCredential("SenderMailAddress","SenderPassword" );
smtp.Credentials = netCre;
try
{
smtp.Send(mail);
}
catch (Exception ex)
{
}