This issue typically arises when an employee who was part of the HR group has left the business, but their user account has not been removed from the group. As the system cannot reach their former work email address, it will try to send the notification to everyone who is part of the group for a number of times.
Although the users are disabled and they are marked as leavers in SelectHR, you need to ensure that the groups assigned to them are removed. This way, when the emails are triggered, the system will not pick their email addresses.
To remove the groups assigned to the users, please follow the below steps.
In the Admin Tool, click User Accounts.
Double click into the relevant user.
Within User Properties, click the Group Memberships tab to expand it.
Select the groups one by one if there are multiple and click Remove.
Click OK to commit the changes.