Notes mail does not generate an alarm trigger for calendar entries created within the alarm window. For instance, I’ve set my alarm preferences for calendar to 180 minutes. If I create an appointment at 2:30pm that starts at 4pm on the same day, no notification will occur.
I’m guessing this is a “feature”, but I can’t find documentation to confirm it. It only becomes an issue for users who want to set alarms way in advance…say 8 hours in advance.