The Exchange and ExchangeWS Plug-ins are so called client-server Plug-ins.
For the smart client to work we need the following server setting:
'Servoy Server Home' > 'Smart Client Settings' > 'servoy.application_server.trustedRemotePlugins' = 'it2be.ExchangeService' or 'it2be.ExchangeWSService' (when you have more Remote Plugins that should be trusted you can make it a comma separated list.