One of the many event notifications that you can enable under your profile icon > My Notifications > Notification Preferences is "Event Modified".
This notification must be enabled along with one of the following conditions:
- You are the event owner
- You are an editor on the event
- You are an admin who is either not limited to specific approval areas or the event has items in your approval area
- You are a sub-admin with access to the approval area that includes one or more of the spaces/resources/service being requested on the event
- The same is true for the "Event Setup Notes Modified" notification.
A modification could be a change to Items - for example removing a Space and adding a different Space
Again, this email notification is sent to All Admins and Sub-Admins who have items to approve within the event, as well as the Event Owner and Event Editor(s).