set or get message-id of send email in c# asp.net

I Am using SMTP to send an email.

My Detail code like this...

public bool sendmail(string From, string To, string CC, string Subject, string Body )
{
try
{
System.Net.Mail.MailMessage objEmail = new System.Net.Mail.MailMessage();
objEmail.Body = Body;
objEmail.From = new MailAddress(From);
objEmail.IsBodyHtml = true;
objEmail.ReplyTo = new MailAddress(To);
objEmail.Subject = Subject;
objEmail.To.Add(new MailAddress(To));

SmtpClient objSmtp = new SmtpClient();

objSmtp.DeliveryMethod = SmtpDeliveryMethod.Network;
objSmtp.EnableSsl = true;

Guid objGuid = new Guid();
objGuid = Guid.NewGuid();
String MessageID = "<" + objGuid.ToString() + ">";
objEmail.Headers.Add("Message-ID", MessageID); //Set Message-ID in Email Header

System.Net.NetworkCredential credentials =new System.Net.NetworkCredential("UserName", "Password");

objSmtp.Credentials = credentials;
objSmtp.EnableSsl = true;
objSmtp.Host = "smtp.gmail.com";
objSmtp.Port = 587;
objSmtp.Send(objEmail);


Page.ClientScript.RegisterStartupScript(this.GetType(), "script", "javascript:alert('Email Sent Successfully');", true);
return true;
}
catch (Exception ex)
{
throw ex;
}
}

In the above code i had set message-id in email header to GUID.But message-id set by me is replaced by email server...

plz help me...