Thread to send Email in Global asax file

Global.asax file --
protected void Application_BeginRequest(Object sender, EventArgs e)
{
Thread td = new Thread(new ThreadStart(SendNotification));
td.IsBackground = true;
td.Start();
}
public static void SendNotification()
{
dbDataContext db = new dbDataContext();
var noti = from n in db.Notificationdbmls
where n.pendingMail == "false"
select n;
if (noti.Count() != 0)
{
try
{
MailMessage mail = new MailMessage();
mail.To.Add(noti.First().ReceiverEmailID);
mail.From = new MailAddress("emailaddress");
mail.Subject = noti.First().Subject;
mail.Body = noti.First().Body;
mail.IsBodyHtml = true;
var client = new SmtpClient("smtpdetails");
client.Credentials = new System.Net.NetworkCredential("emailid", "password");
client.EnableSsl = true;
client.Send(mail);
noti.First().pendingMail = "true";
db.SubmitChanges();
}
catch (Exception ex)
{
//
}
}
}

On aspx page -

On buttonClick -
Notificationdbml nd = new Notificationdbml { Body = body, CreatedDate = DateTime.UtcNow.Date, Description = "", pendingMail = "false", ReceiverEmailID = email, ReceiverUserID = userid, Subject = subject, Type = "User Registration" };
db.Notificationdbmls.InsertOnSubmit(nd);
db.SubmitChanges();

In above SendNotification() code,
after it sends email, immediately, i am changing its status = true;
see the below code -

client.Send(mail);
noti.First().pendingMail = "true";
db.SubmitChanges();