On the Notes client it is possible to set a “Compatibility Mode” to improve the calendar interoperability with other mail clients.
http://publib.boulder.ibm.com/infocenter/domhelp/v8r0/index.jsp?topic=%2Fcom.ibm.help.domino.admin85.doc%2FH_IMPROVING_INTEROPERABILITY_FOR_USERS_OF_OUTLOOK_AND_EXCHANGE_CALENDARS_STEPS.html http://publib.boulder.ibm.com/infocenter/domhelp/v8r0/index.jsp?topic=%2Fcom.ibm.help.domino.admin85.doc%2FH_IMPROVING_INTEROPERABILITY_FOR_USERS_OF_OUTLOOK_AND_EXCHANGE_CALENDARS_STEPS.html
Will this setting works for iNotes too?