Giving me an Error with file attachment using fileupload & failure of a sending mail

protected void btnSubmit_Click(object sender, EventArgs e)
{
   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())); // "
      string path = "~\\File\\" + FileName.Trim(); // "
      lblUpload.Text = "file is uploaded";

      Attachment mail1 = new Attachment(path);  // DirectoryNotFoundException  file or directory cannot be found.

      obj.Attachments.Add(mail1);
   }
   else
   {
      lblUpload.Text = "file not uploaded";
   }

   SmtpClient smt = new SmtpClient();
   smt.Port = 587;
   smt.Port = 465;
   smt.Host = "smtp.gmail.com";
   smt.Host = "smtp.mail.yahoo.com";
   smt.Host = "smtp.live.com";
   smt.EnableSsl = true;
   smt.UseDefaultCredentials = false;
   smt.Credentials = new System.Net.NetworkCredential(txtFrom.Text, txtPwd.Text);

   try
   {
      smt.Send(obj);
   }
   catch(Exception e1)// System.Net.Mail.SmtpException Failur sending mail
   {
      throw e1;
   }
}