public void OnClientConnect(ISocket clientSocket)
        {
            if (_closed)
            {
                return;
            }

            SmtpLog.Info("Client connected");
            ListenForClients();

            var session = new SmtpSession(clientSocket)
            {
                OnMessage = (msg) => _messages.Add(msg)
            };

            session.Start();

            _sessions.Add(session);
        }
 public void Start()
 {
     Listener.Start();
     SmtpLog.Info(string.Format("Server started at {0}", new IPEndPoint(Address, Port)));
     ListenForClients();
 }