Remote event receiver issue

Hi Friends,
I have been working on creating remote event receivers using on premises high trust provider hosted app for one of the share point 2013 default calendar list.
My requirement is to trigger email when a meeting is getting created or updated in the calendar list using remote event receivers.
I have already created the provider hosted app and included remote event receivers and targeted the receiver to work on calendar list using the xml parameter <receivers listurl="lists/calendar"> in elements .xml file.
App is getting deployed successfully to the site and remote event receivers are also getting registered to the calendar list but nothing is happening when i am adding or updating any event in the calendar list