Enables extension objects to enable or disable their modeless windows.
See IExchExtModeless : IUnknown.
HRESULT EnableModeless(
HWND hwnd,
BOOL fEnable
);
Microsoft Exchange uses the IExchExtModeless::EnableModeless method to notify extension objects that they should enable or disable their modeless windows. If an extension has registered for modeless behavior using the IExchExtCallback::RegisterModeless method and has called the IExchExtModelessCallBack::AddWindow method, Microsoft Exchange calls the extension's EnableModeless method when it displays or removes a modal window. In the case of creation, the extension object should disable its modeless windows; in the case of removal, the extension object should enable its modeless windows.