You can setup a sickness trigger notification by doing the following:
Go to Settings and click Notifications.
Click Add Notification in the upper right corner.
Make sure the Type is set to Date.
In the Table drop down, select AbsenceTriggerLink.
In the Field drop down, select End Date.
Click Add Email and locate the correct template (this will need to be created before setting up the notification).
Choose the correct Email Template.
Decide when the email will be sent before or after the trigger is hit.
Click the Recipient dropdown and select one of the options below:
Employee: Email will be sent to the employee who reached a trigger.
Reports To: Email will be sent to the empployee's line manager.
Other: This option enables you to enter a custom email address to which the email will be sent.
(Optional) Click Add to add another recipient as CC.
Click Save.