public static void RetryIfBusy(string server)
        {
            MailAddress from = new MailAddress("ben@contoso.com");
            MailAddress to = new MailAddress("jane@contoso.com");
            MailMessage message = new MailMessage(from, to);
            // message.Subject = "Using the SmtpClient class.";
            message.Subject = "Using the SmtpClient class.";
            message.Body = @"Using this feature, you can send an e-mail message from an application very easily.";
            // Add a carbon copy recipient.
            MailAddress copy = new MailAddress("Notifications@contoso.com");
            message.CC.Add(copy);
            SmtpClient client = new SmtpClient(server);
            // Include credentials if the server requires them.
            client.Credentials = (ICredentialsByHost)CredentialCache.DefaultNetworkCredentials;
            Console.WriteLine("Sending an e-mail message to {0} using the SMTP host {1}.",
                 to.Address, client.Host);
            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);
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine("Exception caught in RetryIfBusy(): {0}", 
                        ex.ToString() );
            }
        }

static void RetryIfBusy( String^ server )
{
   MailAddress^ from = gcnew MailAddress( L"ben@contoso.com" );
   MailAddress^ to = gcnew MailAddress( L"jane@contoso.com" );
   MailMessage^ message = gcnew MailMessage( from,to );

   // message.Subject = "Using the SmtpClient class.";
   message->Subject = L"Using the SmtpClient class.";
   message->Body = L"Using this feature, you can send an e-mail message from an application very easily.";

   // Add a carbon copy recipient.
   MailAddress^ copy = gcnew MailAddress( L"Notifications@contoso.com" );
   message->CC->Add( copy );
   SmtpClient^ client = gcnew SmtpClient( server );

   // Include credentials if the server requires them.
   client->Credentials = dynamic_cast<ICredentialsByHost^>(CredentialCache::DefaultNetworkCredentials);
   Console::WriteLine( L"Sending an e-mail message to {0} using the SMTP host {1}.", to->Address, client->Host );
   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( L"Delivery failed - retrying in 5 seconds." );
            System::Threading::Thread::Sleep( 5000 );
            client->Send( message );
         }
         else
         {
            Console::WriteLine( L"Failed to deliver message to {0}", ex->InnerExceptions[ i ] );
         }

      }
   }
   catch ( Exception^ ex )
   {
       Console::WriteLine(L"Exception caught in RetryIfBusy(): {0}", 
                     ex->ToString() );
   }
   finally
   {
      client->~SmtpClient();
   }
}