try
            {
                client.Send(message);
            }
            catch (SmtpFailedRecipientsException ex)
            {
                for (int i = 0; i < ex.InnerExceptions.Length; i++)
                {
                    SmtpStatusCode status = ex.InnerExceptions[i].StatusCode;
                    if (status == SmtpStatusCode.MailboxBusy ||
                        status == SmtpStatusCode.MailboxUnavailable)
                    {
                        Console.WriteLine("Delivery failed - retrying in 5 seconds.");
                        System.Threading.Thread.Sleep(5000);
                        client.Send(message);
                    }
                    else
                    {
                        Console.WriteLine("Failed to deliver message to {0}", 
                            ex.InnerExceptions[i].FailedRecipient);
                        //Qui raccolgo tutte le mail non inviate
                    }
                }
            }