Getting an error with file attachment in "Attachment mail1 = new Attachment(path);" & throwing an exception in catch block "The operation has timed out." in sending email

MailMessage obj = new MailMessage(txtFrom.Text, txtTo.Text, txtSubject.Text, txtBody.Text);
if (Fileupload1.HasFile)
{
    String FileName = Path.GetFileName(Fileupload1.PostedFile.FileName);
    Fileupload1.PostedFile.SaveAs(Server.MapPath("~\\File\\" + FileName.Trim()));
Fileupload1.PostedFile.SaveAs(Server.MapPath("~\\File\\" + FileName.Trim()));
    string path = "~\\File\\" + FileName;
    lblUpload.Text = "file is uploaded";
  Attachment mail1 = new Attachment(Server.MapPath("~\\File\\" + FileName.Trim())); 
      obj.Attachments.Add(mail1);
}
else {
    lblUpload.Text = "file not uploaded";
}

SmtpClient smt = new SmtpClient("smtp.gmail.com",465 );

smt.EnableSsl = true;
 smt.Timeout = 10000;
smt.UseDefaultCredentials = false;
smt.Credentials = new System.Net.NetworkCredential(txtFrom.Text, txtPwd.Text, "www.gmail.com");

 smt.DeliveryMethod = SmtpDeliveryMethod.Network;
        obj.BodyEncoding = UTF8Encoding.UTF8;
        smt.Credentials = CredentialCache.DefaultNetworkCredentials;

try
{
    smt.Send(obj);
}
catch(Exception e1) // The operation has timed out.
{
    throw e1;
}