If you want to check which of your customers receive a reminder for your appointment, you can use the reminder overview.
Overall Overview
In the "Appointment Confirmations & Reminders" module you will find an overview that shows you how many of your appointments within the last and next 7 days contained a reminder.

Detailed Overview
Next to the pie charts, the number of appointments without a reminder is linked. By clicking on the blue link, you will go to the detailed overview.
In the detailed overview of future appointments, you can quickly and easily set the checkmarks for missing reminders.
