public void SendParallel(MailMessage Message, Sender From, IEnumerable <Recipient> To)
 {
     foreach (var item in To)
     {
         ThreadPool.QueueUserWorkItem(_ => Send(Message, From, item));
     }
 }
 public void Send(MailMessage Message, Sender From, IEnumerable <Recipient> To)
 {
     foreach (var item in To)
     {
         Send(Message, From, item);
     }
 }