Code Not Working Well In Server

Its regarding send mail via c#.net. The following code is working well in my local machine, upload it in server but its not working in server. I m using same smtp server name , email username , password in local and server. But i don't know what is problem? problem is in my coding?

System.Net.Mail.MailMessage objEmail = new System.Net.Mail.MailMessage();
objEmail.From = new MailAddress(dsAdmin.Tables[0].Rows[0]["Emailusername"].ToString());
objEmail.To.Add(To_Tmail.ToString());
objEmail.IsBodyHtml = true;
objEmail.Subject = Subject.ToString();
objEmail.Body = message.ToString() + dsAdmin.Tables[0].Rows[0]["Emailsignature"].ToString();
SmtpClient client = new SmtpClient();
System.Net.NetworkCredential SMTPUserInfo = new System.Net.NetworkCredential(dsAdmin.Tables[0].Rows[0]["Emailusername"].ToString(), dsAdmin.Tables[0].Rows[0]["Password"].ToString());
client.UseDefaultCredentials = false;
client.Credentials = SMTPUserInfo;
client.Host = dsAdmin.Tables[0].Rows[0]["SMTPservername"].ToString();
client.DeliveryMethod = SmtpDeliveryMethod.Network;
client.Port = 587;
try
{
client.Send(objEmail);
res = true;
catch (Exception exc)
{
res = false;
}