protected virtual void OnRaiseEnvelopeEvent(EnvelopeEventArgs e)
        {
            // copy to avoid any chance of race condition
            EventHandler <EnvelopeEventArgs> callEvent = RaiseCustomEvent;

            if (callEvent != null)
            {
                callEvent(this, e);
            }
        }
 // Handle info from publisher
 internal abstract void HandleEnvelope(object sender, EnvelopeEventArgs e);