Once a notification has been set up using the Absence (Employment) table, the emails will be sent out regardless of the status of the sickness.
To check the notifications set up on your system:
Go to Setup and click Settings.
Click Notifications.
There will be a notification called Sickness to be Closed, or with a similar title.
Click this notification to view its settings.
Under Emails you will see when the emails are set to be sent out.
For example, this notification might be set up to be sent out one day before the expected return date on the sickness. In this case, the emails will be sent out even if the sickness is closed because the notification only looks at the expected return date and not the status of the sickness.
📌 Note: It is not possible to change the system so that notifications are not generated for closed sickness.